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KENYA COASTAL DEVELOPMENT PROJECT
Natural Resource Mangement (Componet 2)
Lamu Biodiversity and Ecosystem Health Assessment Technical Report
Research geared towards promoting environmentally sustainable management of
Kenya’s coastal and marine resources
Editors: Victor Mwakha, Judith Okello, Lilian Nduku, Charles Mito, Rashid Anam, Noah
Ngisiang’e.
This report was prepared by Kenya Marine and Fisheries Research Institute (KMFRI). The production
of the report was funded by the Kenya Government, World Bank through Kenya Coastal
Development Project (KCDP).
Copyright © 2015 Kenya Marine and Fisheries Research Institute
Reproduction of this publication for educational or other non-commercial purposes is authorized
without prior written permission from the copyright holder provided the source is fully acknowledged.
Reproduction of this publication for resale or other commercial purposes is prohibited without prior
written permission of the copyright holder.
Cover Image: Field work photos 2014, photos by Milton Apondi and Grifine Nyamongo.
Citation
KCDP, 2015. Lamu Biodiversity and Ecosystem Health Assessment Technical Report: Research
Geared towards Promoting Environmentally Sustainable Management of Kenya’s Coastal and Marine
Resources, KMFRI technical report series, Mombasa, pp.45
Copies are available from:
Kenya Coast Development Project (KCDP)
English Point, Silos Road
P.O.Box 81651/80100 Mombasa
KENYA.
P (+254) 020 8021560/1
F (+254) 020 2353226
E-mail: [email protected]
See more at: http://www.kcdp.co.ke
OR
Director
Kenya Marine and Fisheries Research Institute
P.O. Box 81651–80100
Mombasa, KENYA
Telephone: +254 41 475151/2/3/4/5
FAX: 254 41 475157
E-mail: [email protected]
Internet: http://www.kmfri.co.ke
i
Acknowledgements
We would like to thank the following agencies and people for assistance with the various
aspects of the assessment.
Funding: GEF (Global Environmental Facility)
Research Assistance: Scientists, Technicians, Coxswain, Drivers and technologists from
KMFRI, KWS, local fishermen (Lamu), managers of community conserved areas.
Boat, diving and logistic support: Kenya Wildlife Service (KWS), KMFRI, State
Department of Fisheries (SDF) and Wildwide Fund for Nature (WWF).
Report Writing and Data analysis: Charles Mitto, Judith Okello, Chepkemboi Labbat,
Lilian Nduku, Victor Mwakha, Shaban Mwachireya, Jelvas Mwaura, Amon Kimeli, Charles
Magori, Anthony Nzioka, Boaz Ohowa, Veronica Wanjeri, Linet Kiteresi, Joel Gatagwu,
Noah Ngisiang’e, Harrison Ong’anda, Eric Okuku, Joseph Kamau, Stephen Mwangi.
ii
Table of Contents
Acknowledgements ....................................................................................................................ii
Table of Contents ..................................................................................................................... iii
List of Figures ............................................................................................................................ v
List of Tables ...........................................................................................................................vii
Executive Summary ............................................................................................................... viii
List of Accronyms...................................................................................................................... x
1.
CHAPTER ONE: Introduction ........................................................................................... 1
Objectives ........................................................................................................................... 2
Study Site Description ........................................................................................................ 2
Assessment Strategy ........................................................................................................... 3
2.
CHAPTER TWO: Seagrass Beds ....................................................................................... 5
2.0. Introduction ..................................................................................................................... 5
2.1 Methods ............................................................................................................................ 5
2.2 Results .............................................................................................................................. 6
2.2.1 Water Quality Parameters in Seagrass Beds .............................................................. 6
2.2.2 Seagrass Cover .......................................................................................................... 8
2.2.3 Algal Cover in Seagrass Beds ................................................................................. 10
2.2.4 Seagrass Shoot Density and Canopy Height ........................................................... 11
2.2.5 Macrofauna .............................................................................................................. 12
2.2.6 Fish Diversity in Seagrass Beds .............................................................................. 13
2.3 Discussion ...................................................................................................................... 14
2.4 Conclusion...................................................................................................................... 16
2.5 References ...................................................................................................................... 17
3.
CHAPTER THREE: Coral Reef Ecosystem .................................................................... 20
3.0 Introduction .................................................................................................................... 20
3.1 Methods .......................................................................................................................... 21
3.1.1 Visual Census of Reef Fish Species and Abundance .............................................. 21
3.1.2 Macroinvertebrates .................................................................................................. 22
3.1.3 Coral and Benthic Composition .............................................................................. 22
3.1.4 Coral Species Diversity ........................................................................................... 23
3.2 Results ............................................................................................................................ 23
iii
3.2.1 Water Quality Parameters ........................................................................................ 23
3.2.2 Reef Fish Diversity and Abundance ........................................................................ 25
3.2.3 Coral and Benthic Composition .............................................................................. 26
3.3 Discussion ...................................................................................................................... 29
3.4 Conclusion...................................................................................................................... 30
3.5 References ...................................................................................................................... 30
Appendix .................................................................................................................................. 31
iv
List of Figures
Figure 1.1: Map of the Lamu Archipelago showing the areas sampled during the assessment.
Inset is the map of Kenya highlighting the coastal region and the location of the study site
(red square). ............................................................................................................................... 4
Figure 2.1: Nutrient concentrations in seagrass beds of the areas surveyed in southern part of
Lamu Archipelago ..................................................................................................................... 7
Figure 2.2: Total suspended solids (TSS) and organic matter (OM) concentratios in seagrass
beds of the areas surveyed in the southern part of Lamu Archipelago ...................................... 7
Figure 2.3: Chlorophyll a concentrations in seagrass beds of the areas surveyed in southern
part of Lamu Archipelago .......................................................................................................... 8
Figure 2.4: Proporrtion of seagrass coverage in sampled sites of the southern part of Lamu
Archipelago ................................................................................................................................ 9
Figure 2.6: Georeferenced map of Lamu locating the sampling stations and percentage
seagrass cover of the areas surveyed ......................................................................................... 9
Figure 2.7: Proportion of algal coverage in the different sampling stations of seagrass beds in
the southern part of Lamu Archipelago ................................................................................... 11
Figure 2.8: Average shoot density of seagrasses of the areas surveyed in southern part of
Lamu Archipelago ................................................................................................................... 11
Figure 2.9: Average seagrass canopy height of seagrasses in the sampled sites in Lamu of the
areas surveyed in southern part of Lamu Archipelago ............................................................ 12
Figure 2.10: Macrofauna densities in seagrass beds of the areas surveyed in southern part of
Lamu Archipelago ................................................................................................................... 13
Figure 2.11: Relative fish density (bars indicate standard error) of all species found in the
seagrass beds surveyed in the southern part of Lamu Archipelago ......................................... 13
Figure 2.12: Relative occurrence of different families of fishes found during the survey in the
areas in the seagrass beds in southern part of Lamu Archipelago ........................................... 14
Figure 3.1: Transect layout for coral reef surveys ................................................................... 21
Figure 3.2: Nutrient concentrations in Lamu coral reef areas ................................................. 23
Figure 3.3: Dissolved oxygen and BOD concentrations in Lamu coral reef areas .................. 24
Figure 3.4: Total suspended solids (TSS) and organic matter (OM) in Lamu coral ............... 25
Figure 3.5: Relative fish density in outer reef areas of Lamu .................................................. 26
v
Figure 3.6: Substrate cover in coral reef areas of Lamu. ......................................................... 26
Figure 3.7: Map of hard coral cover around the surveyed sites ............................................... 27
Figure 3.8: Species richness of Scleractinian corals on seven reefs in Lamu. ......................... 28
Figure 3.9: Coral composition as a percentage of all target coral species and groups
encountered during the assesment ........................................................................................... 28
vi
List of Tables
Table 2.1: Seagrass species percentage composition in different sampling locations in Lamu
County ...................................................................................................................................... 10
Table 3.1: Dominance classes for coral abundance ................................................................. 22
vii
Executive Summary
Lilian Nduku, Judith Okello, Victor Mwaka
Assesment of any resource is an important descision making support tool that effectively
guides its sustainable management. The need for biodiversity and productivity assessment of
marine ecosystems is premised by the need to come up management guidelines that suffices
both environmental health and the livelihoods supported by these resources. This technical
report outlines results of a biodiversity assessment of Lamu Archipelago in the nearshore
marine ecosystems (Seagrass and Coral reefs), which was conducted from 6th to 16th April
2014. The survey entailed sampling in various locations within the Southern part of Lamu
Archipelago. The survey focused mainly on two critical nearshore ecosystems (seagrass beds
and coral reefs).
Assesment within the seagrass bed was conducted in 7 sites, namely, Iweni, Tauzi, Wange,
Ntopate, Manda Toto, Manda Maweni and Ngoi. Nine out of the twelve seagrass species
found in Kenya were encountered. The dominant seagrass species T. ciliatum was found to
occur in deeper subtidal areas while the pioneering species occurred in intertidal shallower
areas. Average shoot densities per site ranged from 291 ± 33 shoots m-2 in Tauzi to 865 ± 123
shoots m-2 Ngoi. Canopy heights ranged between 10 ± 0.3 cm in Manda Toto to 18.5 ± 0.5
cm in Ngoi. Few T. gratilla were observed signaling the high densities of seagrass. A total of
48 fish species were indexed. Some of the sites are shielded from human impacts which may
have resulted in the high species diversity and abundances of marine life observed as
compared to some sites suffering from impacts such as seining (Wange), mangrove cutting
and sand harvesting (Ngoi). Further investigations are necessary to assess the fish species
encountered in the Lamu Archipelago.
Sampling in the coral reefs was done along 50 m long transects in seven sites (Iweni, Manda
Toto, Mlango wa Manda, Pezali, Tenewi, Kinyika, Majongoni) covering two habitat types
(exposed and sheltered). Data was collected on coral species diversity, reef fish and coral
benthic composition. Reef health assesesment revealed a poor status with most reef sites
sampled recording less than 20% coral cover. The coral reefs exhibited high dominance of
large coral species such as Porites and Goniastrea and lack of foliose and branching coral
lifeforms, which could be attributed to previous coral degradation induced by likely El Niñorelated warming events. Fish species richness and community composition were comparable
between survey sites with observation of between 26-32 species, and a high of 60 species in
the submerged reef plateau of Tenewi south. This area also had the highest coral benthic
composition. The study established that Local factors such as overfishing and destructive
fishing methods (e.g. use of seine nets) continue to threaten the reef systems and it is likely
they are restricting the recovery of coral from previous bleaching events.
Alongside biodiversity data in the two ecosystems, water quality and hydraudynamics
analysis was done in the same sites. The survey focused on parameters such as nutrient
viii
levels, salinity, suspended sediments and organic matter, current velocities and chlorophyll a.
These data aided in explaining observed biodiversity patterns of these important
coastal/marine ecosystems and associated flora and fauna.
ix
List of Accronyms
BMU
Beach management unit
BOD
Biological oxygen deman
CCAs
Community conserved areas
CTD
Conductivity Temperature and Depth
DO
Dissolved oxygen
KCDP
Kenya Coastal Development Project
KWS
Kenya Wildlife Services
KMFRI
Kenya Marine and Fisheries Research Institute
KMNR
Kiunga Marine National Reserve
LAPSSET
Lamu Port- Southern-Sudan Ethiopian Transport
MPAs
Marine protected areas
OM
Organic matter
TSS
Total suspended solids
x
1. CHAPTER ONE: Introduction
The Kenyan coast constitutes various coastal and marine habitats with diverse and unique
biodiversity including; mangrove forests, seagrass beds and coral reefs, interspersed with
extensive sandy beaches and bottom sand flats and estuarine systems as well as coastal
forests. These environments show strong and consistent seasonal variations in physical –
chemical parameters, driven by the monsoon winds and exposure to river discharge (Obura,
2001, McClanahan, 1988). Such distinct features influence the distribution and productivity
of coastal and marine ecosystems.
These ecosystems provide essential ecological services, and serve as the source of livelihoods
for coastal and inland human populations. However, with increasing population coupled with
potential climate change related effects, coastal and marine ecosystems are continuously
threatened. These threats are causing concern on their biodiversity and productivity and the
livelihoods they support. Lamu Archipelago for instance is one of Kenya’s biodiversity
hotspot not only boasting of the largest continuous mangrove forest patch covering an area of
33,000 ha (Doute et al., 1981) but also biodiversity rich coral reefs and seagrass beds.
The government of Kenya through the Ministry of Transport has initiated the construction of
a port at Manda Bay in Lamu under the Lamu Port- Southern-Sudan Ethiopian Transport(LAPSSET) project. This initiative is also a flagship project under vision 2030 and is
expected to accelerate development of trade routes in the regions traversed by the new
transport corridor. However, the project is also envisaged to result in environmental and
social impacts including loss of natural mangrove habitat, loss of fishing grounds and
pollution. To address such impacts and many more, there is a need to come up with effective
management tools for these ecosystems that ensure that the biodiversity and productivity is
well maintained in order to support the ever increasing demand of local communities.
However, prior to the instigation or employment of appropriate management strategies, there
is a need for providing information on the distribution and status of coastal and marine
ecosystems. It is in line with this that the Kenya Coastal Development Project (KCDP)
supported this biodiversity assessment.
The Government of Kenya received funding from the World Bank in 2011 to catalyse
development activities in the Kenyan Coast.The goal of KCDP is to improve livelihoods of
coastal communities in an environmentally sustainable manner. The Project Development
Objective is to improve management effectiveness and enhance revenue generation of
Kenya’s coastal and marine resources while the Global Environmental Objective is to
strengthen conservation and sustainable use of marine and coastal biodiversity. Part of the
activities to be carried out included biodiversity assessment of marine and coastal resources
both in protected areas and in areas adjacent to them. The Kenya Wildlife Service was
entrusted with spearheading the biodiversity assessment in the marine protected areas
1
(MPAs) while KMFRI conducted the same in areas adjacent to the MPAs. The current
assessment was conducted in Lamu Archipelago in the nearshore marine ecosystems
(Seagrass and Coral reefs). The activity was directly linked to M&E targets 1 and 2 and
indirectly to targets 3 and 4 as outlined below:




Biodiversity management information system to be developed, populated and
updated;
Biodiversity data of targeted areas to be Geo-referenced and updated annually;
Increased number of direct beneficiaries, including percentage of female
beneficiaries;
Increased number of successful community based interventions documented and
disseminated.
Objectives
The knowledge of biodiversity in the Lamu is insufficient yet these ecosystems support most
of the country’s marine species. There exists little information on the status of coral reef and
seagrass bed biodiversity in the area.
The objective of the survey therefore was to identify and quantify the existing flora and
macro fauna in the Southern part of Lamu Archipelago.
This assesment was specifically carried out under the sub-component 2 on environmental and
ecological research in support of natural resource management. The Sub-component is bound by
global objectives namely: 1) Enhanced biodiversity conservation 2) Improved natural resource
governance and 3) Effective involvement of local communities in natural resources management for
improved livelihood.
Study Site Description
Kenya’s coastline spans about 560 km between Vanga in the south and Ishakani in the north
(Fig. 1). The Lamu Archipelago, situated in the North coast of Kenya, is characterized by a
rich biodiversity. The presence of large acreage of continuous mangrove cover approximately 33,000 ha (Doute at al., 1981), coral reefs and seagrass beds makes it a
hotspot for management and conservation efforts. Although on a straight line basis, Lamu
district extends only 138 km southwest from the Somali border, its irregularity and numerous
islands gives it a total coastline length of 560 km. The three biggest islands are Lamu, Pate
and Manda. Except for the south coast of the Islands of Lamu and the southeast coast of
Manda directly exposed to the Indian Ocean, most of the coastal areas in Lamu are covered
with mangrove forests. The area is also characterized by an extensive network of branched
canals scoured by powerful tidal currents which reach inner areas from the bays (Carbone and
Accordi, 2000). In addition is the Kiunga Marine National Reserve (KMNR) which is a
designated UNESCO biosphere reserve and consists of about 50 offshore islands and coral
reefs in the Lamu Archipelago. KMNR has high biodiversity importance due to nesting
2
activities of marine turtles and migratory birds, the presence of whales and some of the
largest area of mangroves in Kenya, and a series of patch and fringing coral reefs around the
barrier islands and on the offshore rocky rock reef (Obura 2001).
With the development of Kenya’s second port at Lamu, the importance of establishing its’
current biodiversity status can not be underestimated. Furthermore, it is important that we
understand how the ecosystems are responding to existing management regimes.
Assessment Strategy
The assessment strategy was determined solely by the local resource users and a Non
Governmental Organisation- World Wide Fund (WWF) regarding reef locations. The surveys
were directed by the locations of the fishing sites indicated by the WWF Project Coordinator
and the local fishermen, and those that would be affected by the development of Kenya’s
second port (Fig. 1.1).
3
Figure 1.1: Map of the Lamu Archipelago showing the areas sampled during the assessment. Inset is the map of
Kenya highlighting the coastal region and the location of the study site (red square).
4
2. CHAPTER TWO: Seagrass Beds
Lilian Nduku, Victor Mwakha, Judith Okello
2.0. Introduction
Seagrasses are marine flowering plants that form an important coastal habitat worldwide. They
are critical components of coastal and marine environments, providing some of the most
economically important ecosystem services of any marine habitat (Costanza et al., 1997; Orth et
al., 2006). They often occur in vast meadows which provide nurseries, shelter, and food for a
variety of commercially, recreationally and ecologically important marine species. In the tropical
and subtropical Indo-Pacific, seagrass meadows are characterized by high species diversity with
mixed vegetation (Hemminga and Duarte, 2000). Twelve genera and 60 species have been
reported worldwide (Short et al., 2007) with twelve species being found in Kenya. Among the
twelve species, Thalassondendron ciliatum is the most dominant one (GoK, 2009). Seagrass
meadows support numerous charismatic faunal species, including turtles, dugongs and seahorses
(Hughes et. al., 2009) as well as associated faunal communities that vary with seagrass species
(De Troch et al., 2001).
The ecological roles of seagrasses can not be undermined owing to their importance as nutrients,
contaminants and sediments filters of estuarine and coastal waters, and their close linkage to
other communities such as coral reefs and mangroves (Nybakken, 2001). The relatively high rate
of primary production in seagrasses drives detritus-based food chains, which helps to support
many organisms (Adam and King, 1995). Seagrasses show clear zonation patterns with water
depth, sediment structure and exposure to air and sunlight during low tide. Species that are
tolerant to exposure are found higher up on the intertidal, while those that cannot withstand
exposure occur submerged in pools of water. Seagrass decline has been reported from various
places around the world (Orth et al., 2006). In Kenya, the major threat has resulted from overexplosion of sea urchins leading to loss of seagrass cover. However, recovery has been evident in
several places.
2.1 Methods
A total of 7 sites were surveyed, namely Kiweni, Tauzi, Wange, Ntopate, Manda Toto, Ngoi and
Manda Maweni (Fig. 1.1). The field survey focused on providing detailed information
(distribution and abundance) on high priority intertidal and shallow subtidal seagrass ecosystems
in the sites. Sampling sites were randomly selected within each site, for assessment but deliberate
attempts made to ensure all suitable/possible seagrass habitats were assessed. Intertidal and sub5
tidal areas were surveyed using boats and by snorkeling. This was done with points and within
transects laid approximately 200 m apart.
Seagrass cover, shoot density and canopy height were determined using standard quadrats for
each parameter described in the SeagrassNet protocol (Short and Coles, 2001) in order to capture
the zonation patterns of seagrass. Within each quadrat, algal percentage cover was also estimated
and species observed noted and identified using identification keys from Oliveira et al. (2003).
At each site, two transects were laid within which parameters were recorded in triplicates after
every 20 m. Seagrass identification was done to the lowest taxonomic level according to Waycott
et al. (2004). Belt transects, 2 m wide were used to determine the densities of macroinvertebrates within the areas studied.
Triplicate surface water nutrient samples, in the seagrass and coral reef sites were collected and
fixed with mercuric chloride before analysis according to the modified spectrophotometric
methods of Parsons et al., 1984. Physicochemical parameters such as temperature, conductivity
and depth were measured using the CTD. Triplicate samples for dissolved oxygen were fixed in
situ before they were analysis by the Winkler method (Parsons, et al., 1984). Total suspended
solids (TSS) were determined in surface water samples collected from the creeks and the Lamu
channel, by filtering a given volume of sea water (depending on the turbidity) on Glass Fibre
Filters (GFF-filters) under low suction. Twenty litres of surface water was filtered using plankton
net of 20 µm mesh size into a receptor bottle attached at the bottom of the plankton net, then
transferred to labelled sample bottles and immediately fixed with Lugol’s Iodine solution for
quantitative analysis in the laboratory, while zooplankton sampling was done by towing twice,
each tow taking 5 - 10 minutes, using a 250 µm mesh size net, and preserved with 5% formalin,
prior to laboratory analyses.
2.2 Results
2.2.1 Water Quality Parameters in Seagrass Beds
Nutrients:
Nutrients concentrations in all the seagrass stations were almost similar, but in most cases the
phosphate (orthophosphate (PO43- -P)) concentrations were higher than those of the other
nutrients types (Nitrates, NO3- -N; and ammonium, NH4+ -N), as depicted in figure 2.1.
6
Figure 2.1: Nutrient concentrations in seagrass beds of the areas surveyed in southern part of Lamu Archipelago
Total suspended solids (TSS) and Organic matter (OM) concentrations
Of all the sampling stations, Wange recorded relatively higher levels of both suspended soilds
and organic matter than the other stations. However, both the total suspended solids (TSS) and
organic matter (OM) concentrations in the seagrass stations, were of simmilar range in all the
stations, with the former values being always higher than the latter (Fig. 2.2).
Figure 2.2: Total suspended solids (TSS) and organic matter (OM) concentratios in seagrass beds of the areas
surveyed in the southern part of Lamu Archipelago
Chlorophyll-a concentrations in seagrass beds
Concentrations of chlorophyll-a in the seagrass beds ranged from approximately 0.03 to 0.06
mg/l. The highest levels were observed at Iweni and while Ntopate had the lowest (Fig. 2.3).
7
Figure 2.3: Chlorophyll a concentrations in seagrass beds of the areas surveyed in southern part of Lamu
Archipelago
2.2.2 Seagrass Cover
Seagrass cover generally increased with distance from the shore with areas experiencing strong
wave activity mainly recording less cover. Additionally, zonation typically exhibited by seagrass
species was observed with opportunistic mixed species occurring in the shallow intertidal areas
while climax monospecific species occurred in the deeper areas. All the sampled sites had
seagrass cover of less than 50% except for Ngoi. The least cover was observed in Tauzi and
Manda Maweni (Fig. 2.4 and 2.5).
8
Figure 2.4: Proporrtion of seagrass coverage in sampled sites of the southern part of Lamu Archipelago
Figure 2.5: Georeferenced map of Lamu locating the sampling stations and percentage seagrass cover of the areas
surveyed
9
Table 2.1: Seagrass species percentage composition in different sampling locations in Lamu County
Site
Seagrass Species percentage composition
Tc
Th
Cr
Cs
Hw
Ho
Hu
29
24
5
19
14
4
5
Tauzi
20
23
17
14
4
Wange
25
25
10
Kiweni
Mto
Pate
12
Manda
Toto
Ngoi
Manda
Maweni
51
17
9
17
34
22
25
42
11
6
11
21
15
Ea
Si
10
12
21
19
11
32
29
35
Cr represents Cymodocea rotundata, Cs - Cymodocea serrulatta; Ea- Enhalus acoroides; Ho - Halophila ovalis; Hs - Halophila
stipulacea Hu - Halodule uninervis; Hw - Halodule wrightii; Si - Syringodium isoetifolium; Tc - Thalassodendron ciliatum; and
Th - Thalassia hemprichii
T. ciliatum was observed mainly in Kiweni, Mto Pate and Ngoi (where it was highest in
proportion). C. serrulatta was observed in all the sites visited while C. rotundata was observed
in all the sites except Wange. H. ovalis was observed in only Kiweni and Tauzi while H.
uninervis was observed only in Kiweni.
2.2.3 Algal Cover in Seagrass Beds
The average algal cover was generally low. Wange had the lowest cover among the sites
sampled, while Mto Pate and Manda Maweni recorded the highest values (Fig. 2.7). The rest of
the substrate with exception of Tauzi, Manda toto and Manda Mawe was covered with sand with
most of the sites having patches of soft coral, hard coral, sponges and ferns. Rocky substrate was
also observed in Manda Mawe and Ngoi.
10
Percentage Algal cover
100
80
60
40
20
0
Kiweni
Tauzi
Wange Mto Pate Manda
toto
Site
Ngoi
Manda
Maweni
Figure 2.6: Proportion of algal coverage in the different sampling stations of seagrass beds in the southern part of
Lamu Archipelago
2.2.4 Seagrass Shoot Density and Canopy Height
Average seagrass shoot density
(individuals/m2)
Figure 2.8 shows the average shoot density of seagrass in the various sampling locations. On
average, Ngoi site displayed the highest density of shoots (865 ± 123 individuals/m 2) followed
by Wange (630 ± 100 individuals/m2). Tauzi site had the lowest average density of seagrass (291
± 33 individuals/m2).
1200
1000
800
600
400
200
0
Kiweni Tauzi Wange
Mto
Pate
Site
Manda
Toto
Ngoi
Manda
Maweni
Figure 2.7: Average shoot density of seagrasses of the areas surveyed in southern part of Lamu Archipelago
11
Average seagrass canopy height (cm)
Ngoi had seagrass with the highest canopy height range (18.5 ± 0.5) followed by Ntopate (15.1 ±
0.4 cm). Manda Toto site had the lowest caopy height range (Fig. 2.9).
25
20
15
10
05
00
Kiweni
Tauzi
Wange
Mto Pate
Manda
toto
Ngoi
Manda
Maweni
Site
Figure 2.8: Average seagrass canopy height of seagrasses in the sampled sites in Lamu of the areas surveyed in
southern part of Lamu Archipelago
2.2.5 Macrofauna
Mto Pate was observed to have the highest density of macrofauna among the sites sampled
followed by Manda Maweni (Fig. 2.10). Tauzi and Wange had the lowest macrofaunal counts
(15 ± 1 and 12 ± 3 individuals/m2 respectively).
12
Average individuals/m2
120
100
80
60
40
20
0
Kiweni
Tauzi
Wange
Mto
pate
Site
Manda
toto
Ngoi
Manda
maweni
Figure 2.9: Macrofauna densities in seagrass beds of the areas surveyed in southern part of Lamu Archipelago
2.2.6 Fish Diversity in Seagrass Beds
Relative Fish Density (No.s/250m2)
A total of 48 species belonging to 19 families were recorded; all being bony fishes (Class
Osteichthyes) (Table S1). Relative fish abundance in seagrass beds was high in Pate Island, with
Ntopate near Shanga (recording 150 individuals per 250 m2 followed by Kiweni near Parzali
recording 139 individuals per 250 m2. Ngoi near Kipungani and Wange recorded the lowest fish
abundance estimates of 45 and 34 individuals per 250 m2 respectively (Fig. 2.11).
200
180
160
140
120
100
80
60
40
20
0
Kiweni
Manda Toto
Ngoi
(Kipungani)
Ntopate
(Shanga)
Tauzi
Wange
Survey Sites
Figure 2.10: Relative fish density (bars indicate standard error) of all species found in the seagrass beds surveyed in
the southern part of Lamu Archipelago
13
In terms of species richness, the highest number of taxa (33 species) was observed at Ntopate
(Shanga) followed by Kiweni (27 species) while at Wange only 10 species were observed. Ngoi
and Tauzi only had 14 and 15 species respectively observed during the same survey.
Angelfishes, butterfly fishes were observed at Ntopange and Kiweni only, whereas the emperors,
rabbitfishes, parrotfishes and wrasses were observed in all of the surveyed sites (Fig. 2.12).
Cardinalfishes were only seen at Ngoi during the survey.
Angelfishes
Breams
Butterflyfishes
Cardinal fishes
Damselfishes
Emperors
Goatfishes
Gobies
Grunters
Mojarras
Parrotfishes
Rabbitfishes
Sandperches
Snappers
Surgeonfishes
Sweetlips
Triggerfishes
Wrasses
Relative occurrence per 250m2
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Kiweni
Manda Toto
Ngoi
(Kipungani)
Ntopate
(Shanga)
Tauzi
Wange
Survey Sites
Figure 2.11: Relative occurrence of different families of fishes found during the survey in the areas in the seagrass
beds in southern part of Lamu Archipelago
2.3 Discussion
This was the the first ever detailed assessment of the seagrasses in the Lamu County under the
KCDP project. A total of 7 sites were surveyed including Kiweni, Tauzi, Wange, Mto Pate,
Manda Toto, Ngoi and Manda Maweni. A total of 9 out of the possible 12 seagrass species were
observed in the shallow intertidal areas. The substrate was mainly covered with multispecies
seagrass communities in the shallow intertidal zones while those found in deeper areas consisted
mainly of monospecific communities. Continuous seagrass communities were mainly observed
although fragmented communities were also common. The substrate type was generally observed
14
to determine the cover – either seagrass, coral (hard and soft), or algae. Generally, rocky
substrates were characterized by algae and few seagrass cover while sandy substrates were
mainly composed of seagrass species. Seagrasses were also observed to grow in hard and soft
coral substrate areas.
Ngoi and Manda Toto were observed to display the highest proportion of seagrass cover while
Manda Maweni and Tauzi displayed the lowest. Manda Toto was dominated by, T. hemprichii,
C. rotundata, C. serrulatta and H. wrighttii were observed while in Ngoi, T. ciliatum, S.
isoetifolium, C. serrulatta and C. rotundata were mainly observed. This could be due to the fact
that on average most pioneering species were observed in these sites. Additionally, rocky
substrate was encountered in some areas especially in Ngoi and Manda Maweni.
All identified seagrass habitats had high ecological value in supporting biodiversity. Mto Pate
and Manda Maweni for instance had the highest number of macrofaunal counts in comparison to
the other sites visited. This could be explained by the high seagrass cover in these areas a feature
which is known to support high macroinfauna (Muthama and Uku, 2003).
The health of seagrass species in most of the sites visited was observed to be averagely good, as
shown by the high coverage of seagrass, high seagrass shoot densities, diversity and averagely
high canopy height. Despite the fact that macrofaunal counts were equally high in many sites
(e.g. Manda Maweni and Mto Pate), it was observed that the sea urchins that feed on seagrass
beds were few. Only Echinometra mathaei was encountered in Kiweni and Mto Pate.
Tripneustes grattilla which are known to decimate large areas of seagrass during their blooms,
though observed during the survey were not encountered in transects.
The management of Lamu should ensure that these ecosystems are protected from potential
threats such as overfishing and sea urchin herbivory. Increase in sea urchins (T. gratilla) can
have devastating effects diminishing seagrass cover, distribution and health. Recently, for
instance, T. gratilla explosion triggered by eutrophication and reduced predation by fish has led
to massive decline of seagrass beds in Kenya (e.g. Eklöf et al., 2008; Harmelin-Vivien, 1985).
The biodiversity survey revealed differences in fish assemblages for the different sites sampled
in Lamu. In total, 48 species were recorded in seagrass beds. The structure of the fish
communities provides insights into human impacts on the environment as reflected in the distinct
differences in fish communities between sites. At Kiweni for example, community conservation
efforts, in general, assist in maintaining a high species richness and fish abundance. On the other
hand, at Ntopate, in as much as there is no community conservation effort, there was also high
fish species diversities and abundance. However, fish densities and species diversities were low
in the sheltered side at Ngoi and Wange. Ngoi near Kipungani was observed to be a site that
once used to be rich in corals as it is a mixture of both seagrass and small coral head patches all
over the place. The degradation of the site is thought to be as a result of human disturbances
15
landwards (sand harvesting and mangrove cutting) which seem to have an impact on the marine
habitat hence the low fish densities and diversities.
In terms of trophic groups, most of the species were invertebrate feeders taking advantage of
invertebrates that use seagrass beds as sites for refuge. Other species encountered took advantage
of both the animal and plant material found in seagrass sites while others were herbivores solely
relying on the seagrass and phytoplankton present. Families like the angelfishes and
butterflyfishes observed are species of aquarium importance and were found during the study at
Kiweni and Ntopate, although they are not limited to these two sites. In contrast, emperors,
rabbitfishes, parrotfishes and wrasses were observed at all sampling sites and are important food
fishes.
According to the IUCN Red list status, the species observed during the survey were classified as
species of least concern (LC) or having not yet been evaluated (IUCN Red list, 2014). However,
when one looks at the population trends of the fish species observed, Chaetodon auriga
(Threadfin butterflyfish) belongs to a list of species whose population is decreasing as though no
species specific conservation measures have been put into place. This species of fish is mostly
harvested by artisanal and aquarium fishes along the Kenyan coast (Mangi and Roberts, 2006).
The development of the proposed Lamu Port-Southern Sudan-Ethiopia Transport project
(LAPSSET) project is expected to cause potential threats to seagrass beds arising from
destruction due to oil spills, eutrophication and sedimentation. Sedimentation and eutrophication
have been sited as the major cause of seagrass loss globally (Björk et al., 2008). It is
recommended that monitoring should be conducted annually and seasonally so that the impact of
port development on seagrass beds is ascertained. Such data can inform stakeholders and the
management and measures can be taken to ensure that seagrass are managed to ensure continued
ecosystem service provision. Management plans should also focus on ensuring that local
communities and stakeholders are sensitized about the importance of seagrass ecosystems in
ecosystem services provision to prevent their loss. If such measures are taken into account,
seagrass beds will be resilient to potential impacts of climate change which while interacting
with natural and anthropogenic effects could lead to irreversible change in biodiversity impacting
directly or indirectly to ecosystem services (Björk et al., 2008).
2.4 Conclusion
The study encountered nine out of twelve seagrass species found in Kenya. The dominant
seagrass species T. ciliatum was found to occur in deeper subtidal areas while the pioneering
species occurred in intertidal shallower areas. Few T. gratilla were observed signaling the high
densities of seagrass. As such, development of management plans for Lamu area should focus on
maintaining seagrass cover for continued provision of ecosystem services. Further, regular
16
monitoring of seagrass biodiversity supplemented with regular stakeholder dissemination is
recommended to ensure sustainable management of these resources such that seagrasses are
resilient to emerging threats such as Port development, effects of climate change and sea
urchin/fish herbivory.
This first survey of fish species richness in seagrass beds in Lamu. Despite an underestimation of
small cryptic species that were not taken into account, 48 species were indexed in just 10 days of
observation. Some of the sites have been shielded from human impacts resulting in higher
species diversity and abundances compared to some sites suffering from impacts such as seining
(Wange), mangrove cutting and sand harvesting (Ngoi). Further investigations of fish species
occuring within seagrass meadows are necessary for the Lamu Archipelago region.
2.5 References
Adam, P. and King, R. J., 1995. Ecology of unconsolidated shores. In Biology of Marine Plants,
M.N. Clayton and R.J. King, editors. Longman Australia Pty Limited, Melbourne, pp.
296-309.
Björk, M., Short, F., Mcleod, E., Beer, S., 2008. Managing seagrasses resilience to climate
change. S. Björk M Short F Mcleod E And Beer, ed. IUCN, Gland, Switzerland. 56pp.
Costanza, R., d’Arge, R., de Groot, R., Farber, S., Grasso, M., Hannon, B., Limburg, K., Naeem,
S., O’Neill, R., Paruelo, J., Raskin, R., Sutton, P. and van den Belt, M., 1997. The value
of the world’s ecosystem services and natural capital. Nature 387: 253-260.
De Troch, M., Fiers, F., Vincx, M., 2001. Alpha and beta diversity of harpacticoid copepods in a
tropical seagrass bed: the relation between diversity and species’ range size distribution.
Marine Ecology Progress Series 215, 225–236.
Eklöf J, M., Delatorrecastro, Gullstrom, M., Uku, J., Muthiga, N., Lyimo, T. and Bandeira, S.
2008. Sea urchin overgrazing of seagrasses: A review of current knowledge on causes,
consequences, and management. Estuarine, Coastal and Shelf Science 79 (4)
(September): 569-580.
English, S., Wilkinson, C and Baker, V. 1997. Survey manual for tropical marine resources, 2nd
edition. Australian Institute of Marine Science (Townsville).
Fowler, J. 1987. The development of sampling strategies for population studies of coastal reef
fishes. A case study. Coral Reefs, 6, 49 – 58.
17
Gaines, William L., Harrod, Richy J., Lehmkuhl, John F., 1999. Monitoring biodiversity:
quantification and interpretation. Gen. Tech. Rep. PNW-GTR-443. Portland, OR: U.S.
Department of Agriculture, Forest Service, Pacific Northwest Research Station. 27 p.
Gillibrand, C. J., Harris, A. R. Mara, E., 2007. Inventory and spatial assemblage study of reef
fish in the area of Andavadoaka, South-West Madagascar (Western Indian Ocean).
Western Indian Ocean Journal of Marine Science, 6(2), 183 – 197.
Government of Kenya, 2009. State of the Coast Report : Towards Intergrated Management of
Coastal and Marine Resources in Kenya. National Environment Management Authority
(NEMA), Nairobi. 88pp.
Hammer, Ø., Harper, D.A.T., Ryan, P.D., 2001. PAST: Paleontological statistics software
package for education and data analysis. Palaeontologia Electronica 4(1):
9pp. http://palaeo-electronica.org/2001_1/past/issue1_01.htm
Harmelin-Vivien, M. L., 1979. Ichtyofaune des récifs coralliens en France Outre-Mer. ICRI.
Doc. Secrétariat d’Etat à l’Outre-Mer et Ministère de l’Aménagement du Territoire et de
’Environment. 136 pp.
Harmelin-Vivien, M.L., Harmelin, J., Chauvet, C., Duval, C., Galzin, R., Lejeune, P., Barnabé
G., Blanc, F., Chevalier, R., Duclerc, J., and Lasserre, G., 1985. Evaluation visuelle des
peuplements et populations de poissons: méthodes et problèmes. Rev. Ecol. Terre Vie 40:
467–539.
Hemminga M.A. & Duarte C.M., 2000. Seagrass Ecology. Cambridge University Press
Cambridge.
Hughes, A.R., Stochowicz, J.J. & Williams, S.L., 2009. Morphological and physiological
variation among seagrass (Zostera marina) genotypes. Oecologia. 159, 725–733.
Mandima, J., Mwima, H., 2005. Baseline fish biodiversity surveys – Experiences from the
Zambezi River, Southern Africa.AWF Conservation in Practice Papers, July, 2005. 7pp.
McClanahan, T. R., 2005. Recovery of carnivores, trophic cascades and diversity in coral reef
marine parks. In: Ray, J.C., Redford, K. H., Steneck, R. S., Berger, J. (Eds). Large
carnivores and the conservation of biodiversity. Island Press. Washington DC., USA
McClanahan, T. R., 2008. Food-web structure and dynamics of East African coral reefs. In:
McClanahan, T. R. and Branch, G. M. 2008. Eds. Food webs and dynamics of marine
reefs. Oxford University Press Inc., New York, USA
18
McClanahan, T.R. 1988. Seasonality of East Africa’s coastal waters. Marine Ecological
Progress Series, 44, 191 – 199.
Muthama C.M. and Uku, J.N., 2003. Macrofaunal assemblages of littoral seagrass communities.
Jan H. and Nyawira M. (Eds.). Recent Advances in Coastal Ecology. African Studies
Centre Research Report 70, 51-63.
Nybakken, J.W., 2001. Marine Biology: An Ecological Approach. Benjamin Cummings. San
Fransico.
Okemwa, G.M., Nzuki, S. and Mueni, E., 2005. The status and conservation of sea turtles in
Kenya. Marine Turtle Newsletter, 105, 1 – 6.
Oliveira, E., C., Österlund, K., and Mtolera, M. S. P., 2003. Marine plants of Tanzania : A field
guide to the seaweeds and seagrasses of Kenya and Tanzania
Orth, R. J., Carruthers, T. J.B., Dennison C. W., Duarte, C. M., Fourqurean,J. W., Heck Jr., K.
L., Hughes, A. R., Kendrick,G. A., Kenworthy, W. J., Olyarnik, S., Short F. T., Waycott,
M., and Williams, S. L., 2006. Global Crisis for Seagrass Ecosystems. Bioscience
Articles. 56 (12), 987-996.
Short FT, Carruthers TJB, Dennison WC, Waycott M. 2007. Global seagrass distribution and
diversity: A bioregional model. Journal of Experimental Marine Biology and Ecology.
350:3–20.
Short. F. T. and Coles, R. (eds.) 2001. Global Seagrass Research Methods. Elsevier Publishing,
The Nertherlands, 482 pp. ISBN:0444508910.
Waycott, M., McMahon, M., Mellors, J., Calladine, A., Kleine, D. (2004). A guide to the tropical
seagrasses of the Indo-West Pacific. Townsville: James Cook University, 72pp.
19
3. CHAPTER THREE: Coral Reef Ecosystem
Shaban Mwachireya, Jelvas Mwaura
3.0 Introduction
Coral reefs play an important role for a range of marine organisms. Their intricate physical
structure provides an ideal setting for a system of complex ecological interactions, thus making
them a good source of food and shelter for marine organisms. Coral reefs comprise a high
diversity of organisms including: hard and soft corals of various sizes and morphologies; their
symbiotic dinoflagellate microalgae (zooxanthellae); coralline and other macroalgae; and
invertebrates and fish. The structure and position of coral reefs along tropical coastlines protect
these coasts from storms, flooding and erosion, at the same time enabling formation of associated
seagrass and mangrove ecosystems (Hoegh-Guldberg, 1999). Addintionally, coral reefs are a
source of resources for many coastal communities. For instance, calcified corals are mined and
processed to produce building blocks and lime for construction. Coral reefs are also major tourist
attractions (Hawkins and Roberts, 1994; Wilhelmsson et al., 1998), with coral reef tourism alone
generating billions of dollars (Hoegh-Guldberg, 1999). Coral reef fisheries are even more
important (Russ, 1991), yielding at least 6 million metric tonnes of fish catches worldwide
annually (Munro, 1996). In Tanzania, for example, over 90% of the marine fisheries are
artisanal, focusing on coral reef fish (Jiddawi and Öhman, 2002). Besides finfish, coral reefs are
fishing grounds for cephalopods, gastropods, echinoderms and bivalves.
The Lamu Archipelago is of high biodiversity importance due to a series of patch and fringing
coral reefs around the barrier islands and on the offshore rocky rock reef (Obura, 2001). The
coral reefs of this area are transitional with the reefs on the Somali coast and the upwelling
system to the north (Carbone and Accordi 2001). Biogeographically, reefs in the area have
however lower species diversities than those further south of the Kenyan coastline (Yaninek,
1978; McClanahan, 1990). Most reef systems are considered to be under high potential threat,
with impacts including overfishing, destructive fishing methods and coral bleaching (Wilkinson
and Souter, 2008). Lamu Archipelago specifically has been designated for extensive port-related
development, which is likely to affect the distribution and abundance of reef biodiversity through
coastal development resulting into increased sedimentation.
A major impediment to biodiversity conservation and management in the lamu region is
inadequate information on marine biodiversity (their status and distribution) to guide planning.
This study focussed on detailed biodiversity assessment of nearshore reefs of lamu region
because of their important ecological functions and their socio-economic significance.
20
3.1 Methods
Seven reef sites of two habitat types (exposed or sheltered) were selected for surveys (Fig. 1.1).
Sheltered sites were identified as being within a protected system such as a lagoon or leeward
side of an island/reef with relatively low wave energy. Such reefs were mainly behind barrier
reefs or tucked inside a bay. Exposed sites were those with high wave energy and generally were
on outer slopes of barrier reefs and fringing reefs on the windward side of islands/reefs.
Deliberate attempts were made to choose the two contrasting sties (exposed and sheltered
habitats) close to each other and each othe two to be surveyed on each day to provide a general
overview of both habitat types in each region. Where this was not possible, only one habitat type
was surveyed, whichever of these the reef topography allowed. Biological data (fish,
invertebrates and benthic groups) was collected in replicate 50 m transects, laid across hard
substratum areas of the site. A tape measure was secured at the starting point using a piece of
metal-rebar wedged into rock by the transect layer. The fish surveyor always went ahead of the
other surveyors in order to avoid fish being scared away, which would add bias to the data. The
location of each sampling site identified was geo-referenced using hand held GPS (Garmin).
3.1.1 Visual Census of Reef Fish Species and Abundance
In each site, 3 transect lines of 50m length were laid out and fish census for abundance and
diversity carried out within 2.5 m of either side of the transects (Fig. 3.1). Transects were laid
randomly along the reef slope within a depth range of 2–4 m, averaging 3 m. To measure the
diversity of reef fishes, a recent method designed by Samoilys and Randriamanantsoa (2011) for
biogeographic analysis of species distributions in the WIO was adopted. It is based on
compilation of a complete species inventory of 19 common families at each site, recognized as
being good indicators of fishing pressure, aquarium collections and reef health. Each transect
took an average of eight minutes to complete. The species of fish recorded during along each
transect were combined to give a species list for each site.
Figure 3.1: Transect layout for coral reef surveys
21
3.1.2 Macroinvertebrates
Macroinvertebrate counts were conducted along the same 50 m length transects, with the
observer recording observed invertebrate species within 2.5 m to either side of the transect lines.
3.1.3 Coral and Benthic Composition
Benthic community structure at each sampling location was assessed using still photographic
frame assessment technique where each frame was taken approximately 0.6 m above the
substratum and just to the side of the tape. 40 digital photos were taken at half meter interval
along the 50 m transect used in fish census (Osborne et al., 2013). The photos were later
downloaded into a computer and benthos analysed using a visual basic program, Coral Point
Count estimate (CPCe) with excel extensions Kohler and Gill, 206). A matrix of randomly
distributed points were overlaid on an image, and the species or substrate-type lying beneath
each point identified visually as being hard coral, soft coral, sand, rubble, seagrass, sponge,
fleshy algae, and turf algae.
Proportional abundance of all genera at a site was estimated on a five-point scale towards the end
of the dive. Table 3.1 below shows how the coral abundance index will be assigned at each site
during data analysis.
Table 3.1: Dominance classes for coral abundance
Code
Class
Explanation
Numerical (approximate)
5
Dominant
Dominate the coral community >30% of coral cover
and/ or structure of the site
4
Abundant
Visually abundant and seen in 10-30% coral population by number or area
large numbers. Co-dominate and/or large number of colonies (>100)
the site
seen/inferred in the immediate area of the site
(2500 m2)
3
Common
Easily found/seen on site, but >1% of coral population by number or area
not dominant in any way
and/or >20 colonies seen/inferred in the
immediate area of the site (2500 m2)
2
Uncommon/O
ccasional
Not easily found, but several <10 colonies seen/inferred in the immediate
individuals seen or can be area of the site (2500 m2)
found by dedicated searching.
1
Rare
Found by chance occurrence <2 colonies seen/inferred in the immediate
or only 1 or 2 found by area of the site (2500 m2)
dedicated searching.
22
3.1.4 Coral Species Diversity
Hard coral diversity surveys began once the benthic cover surveys at each site were complete.
Hard coral genera diversity was determined by searching either side of the transect line, usually
in a zigzag pattern along the transect tape. If the observer was uncertain of a species, the coral
was photographed to assist with subsequent indentification based on tradional morphologiacallybased systematic framework of veron (2000). In addition, the survey gathered data on affected
corals from mass coral bleaching event which affected the Kenyan coral reefs between March
and April 2014.
3.2 Results
3.2.1 Water Quality Parameters
Nutrients
The nitrate concentrations [NO3- -N] were higher than phosphates (orthophosphate) and
ammonium in all the stations, as shown in figure 3.2.
Figure 3.2: Nutrient concentrations in Lamu coral reef areas
23
Disssolved oxygen (DO) and Biochemical oxygen demand (BOD) – Coral reefs
The DO and BOD concentrations at Iweni, Manda toto and Tauzi had similar trends, i.e., the DO
levels were higher than the BOD levels, but at Mlango wa manda and Pezari the levels of DO
and BOD were almost similar (Fig. 3.3).
Figure 3.3: Dissolved oxygen and BOD concentrations in Lamu coral reef areas
Total Suspended Solids and Organic Matter
The total suspended solids concentrations varied considerably with Manda maweni recording the
highest levels (Fig. 16). Organic matter concentration levels were lower than TSS in all the
stations, the lowest values being observed at Manda maweni (Fig. 3.4).
24
Figure 3.4: Total suspended solids (TSS) and organic matter (OM) in Lamu coral
3.2.2 Reef Fish Diversity and Abundance
Fish Diversity
A total of 68 fish species was observed, representing 40 fish families recorded across the seven
sites. The highest diversity per location, 60 species, was recorded at Tenewi south, a submerged
reef plateau. Diversity was also notably high on the extensive reef of Iweni and Manda-toto. The
least number of fish species was recorded at Majoongoni (17 species) and Mlango- manda (18
species).
Fish Abundance
Reef fish family abundance was highly variable between survey sites, with Iweni having the
highest levels 550 per 250 m2. The largest contribution to abundance was recorded for
Acanthuridae and Lutjanidae. The second largest contribution to abundance was from the
Labridae and Pomacentridae. The remaining abundance is predominantly comprised of Scarids,
Chaetodontids and Serranids (Fig. 3.5).
25
Figure 3.5: Relative fish density in outer reef areas of Lamu
3.2.3 Coral and Benthic Composition
Hard coral cover was variable at all survey sites with the highest levels found in Tenewi south
(44%), followed by Tenewi south and Kiweni with similar cover of 21-25%). Kinyika outer and
Pazali rock had lowest coral cover, which were all exposed locations (Fig. 3.6 and 3.7). Macro
algae were more dominant in Majongooni and Manda-toto (39%, and 23% respectively).
Figure 3.6: Substrate cover in coral reef areas of Lamu.
26
Figure 3.7: Map of hard coral cover around the surveyed sites
Coral Diversity
The coral species diversities per site ranged between 104 and 150. 32 genera and 64 species of
recruits were observed. Manda Toto and Tenewi North sites had the highest numbers of coral
generas while Mlango wa Manda had the least diversity (Fig. 3.8).
27
30
Coral genera
25
20
15
10
5
0
Kiweni
Kiweni chini
Manda
Toto
Mlango wa Pazali Rock
Manda
Tenewi
north
Tenewi
south
Sites
Figure 3.8: Species richness of Scleractinian corals on seven reefs in Lamu.
Coral genera abundance
The most dominant corals at most sites were Porites and Echinopora, followed by Goniastrea and
Pocillopora (Fig. 3.9).
Figure 3.9: Coral composition as a percentage of all target coral species and groups encountered during the
assesment
28
3.3 Discussion
This survey provided a highly detailed baseline assessment of the status of the coral reefs in
Lamu. The results on status generally depict an area with relatively poor reef health conditions
with low coral cover. Typical coral cover on most reefs was below 20%, with high coverage of
erect fleshy algae, above 18% and algal turfs covering above 44%. The exceptions with high
coral cover were Tenewi south and Tenewi north, an off shore submerged reef plateau (44%).
The values seen at Tenewi areas are similar to those of offshore patch reefs, where fishing level
is low and bleaching of coral is minimal. Sites that exhibited high percentage coral abundance
generally displayed high generic scleractinian diversity. Although reefs had low coral
abundance, they exhibited high dominance of large coral species such as Porites and Goniastrea
and lack of foliose and branching coral lifeforms, which could be attributed to previous coral
degradation induced by likely El Niño-related warming events (Obura 2003).
Reefs grow best in waters that have naturally low concentrations of nutrients (nitrogen and
phosphorus) and sediments. With continuous disturbances from natural and human impacts, they
may fail to regenerate leading to their loss (Cornel, 2007). The effects of sedimentation and
eutrophication are considered insidious particularly in comparison to fishing and climate change
impacts, but increase in sediment loads and nutrient may interact with other threats to cause
habitat degredation (Cornel, 2007). Bleaching events lead to change in community structure of
reefs or loss of coral cover although the factors that lead to this are difficult to identify due to
insidious effects of declining water quality with detrimental effects on tourism and fisheries
(Pandolfl et al., 2005; Cornel, 2007). The concentrations of nutrients (nitrogen and phosphorus)
were relatively low in this study, implying good water quality suitable for growth of corals.
Fish species richness and community composition were comparable between survey sites with
observation of between 26-32 species, with an exception of two sites that had higher diversity of
42 and 60 species. Further examination of the species composition shows fish families such as
Acanthuridae, Labridae and Pomacentridae account for a large proportion of this abundance. The
observed patterns of fish species community composition are also similar to those from southernfished reefs in Kenya (McClanahan et al., 2006b), Mauritius and Seychelles (Graham et al.,
2005; Ahamada et al., 2008). Commercially important fish families such as serranidae,
Lutajanidae, Haemulidae and Mullidaae were rarely seen on most reefs, indicating high fishing
pressure. However, relatively high numbers of commercilal fish families were found at Iweni (a
proposed community protected area) and Tenewi, (an offshore reef) suggesting effectiveness of
establishing or strengthening community-protected areas in reducing fishing pressure commonly
observed on nearshore reefs due to their easy accessibility. To help in reversing any decline, we
should act to reduce all threats, reefs should be managed as entire ecosystems and reef
management should focus on having clear conservation goals such that success can be defined or
measured (Pandolfi et al., 2005).
29
3.4 Conclusion
This work has highlighted local and regional stress associated factors that threat the health and
biodiversity of Lamu’s coral reefs. Local factors such as overfishing and destructive fishing
methods (e.g. use of seine nets) continue to threaten the reef systems and it is likely that they are
restricting the recovery of coral from previous bleaching events. It is therefore essential that
every effort is made to minimise these impacts through appropriate mitigations measures that
promote coastal and marine biodiversity conservation. Conservation recommendation includes
finding a suitable locality where corals at Kiweni can be replanted. This is particularly important
in light of the significant impact from port development that is set to take place in the area this
year.
Tenewi reefs are shown to be the best reefs in Lamu, containing high coral abundance and
diversity. This area should be earmarked for protection of biodiversity and act as source of coral
larvae to other areas that are degraded.
The baseline data now available will be invaluable for ongoing monitoring of the same reefs to
assess the impact of future coastal development such as port construction on nearby reefs and
management initiatives suggested in Tenewi.
3.5 References
Osborne, K., Miller, I., Johns, K., Jonker, M., Sweatman, H., 2013. Preliminary report on
surveys of biodiversity of fishes and corals in Torres Strait. Report to the National
Environmental Research Program. Reef and Rainforest Research Centre Limited, Cairns
(33pp.).
Veron, J.E.N., 2000. In: Stafford-Smith, M (ed) Corals of the World, 3 vols. Australian Institute
of Marine Science, Townsville
Veron, J.E.N., 2000. In: Stafford-Smith, M (ed) Corals of the World, 3 vols. Australian Institute
of Marine Science, Townsville
30
Appendix
Table S1: Fish family contribution to the species list at each site
Family
Iweni
Kinyika outerMajongooniManda-Toto
Mlangoni-Manda
Pezali Rock Tenewi North Tenewi SouthGrand Total
Acanthuridae
3
3
3
9
3
3
7
14
45
Balistidae
2
2
3
2
9
Caesionidae
1
1
1
3
Carangidae
2
2
Chaetodontidae
2
2
3
6
3
1
8
25
Ephippidae
1
1
Haemulidae
3
3
4
2
9
10
31
Holocentridae
1
1
3
1
6
Kyphosidae
2
1
2
5
Labridae
3
3
3
3
3
4
6
25
Lethrinidae
2
3
1
1
7
Lutjanidae
3
2
3
2
2
8
20
Mullidae
1
1
1
2
3
8
Platycephalidae
1
1
Pomacanthidae
2
2
6
1
2
3
16
Pomacentridae
3
4
2
3
3
15
Scaridae
3
1
2
3
2
1
1
5
18
Serranidae
2
2
1
1
1
7
Siganidae
1
3
3
3
10
Tetraodontidae
1
1
2
Zanclidae
3
3
6
Total
38
32
17
42
18
26
29
60
262
Table S2: fish species observed during the Lamu biodiversity assessment survey of April 2014 (from depths of 0 – 5
m).
Species
Trophic
group
Canthuridae
Species……………………...Trophic group
Chaetodontidae
Acanthurus auranticavus
Detritivore
Chaetodon auriga
Invertivore
Naso brevirostris
Herbivore
Chaetodon vagabundus
Omnivore
Apogonidae
Gerreidae
Apogon aureus
Invertivore
Gerres oyena
Cheilodipterus quinquelineatus
Invertivore
Gobiidae
Balistidae
Rhinecanthus aculeatus
Invertivore
Invertivore
Amblyeleotorius wheeleri
Invertivore
Amblygobius albimaculatus
Invertivore
31
Species
Trophic
group
HAEMULIDAE
Species
Trophic
group
MULLIDAE
Plectorhinchus gaterinus
Invertivore
Parupeneus barberinus
Plectorhinchus orientalis
Invertivore
NEMIPTERIDAE
Scolopsis ghanam
LABRIDAE
Invertivore
Invertivore
Cheilinus chlorurus
Invertivore
PINGUIPEDIDAE
Cheilio inermis
Invertivore
Parapercis hexopthalma
Coris formosa
Invertivore
POMACANTHIDAE
Halichoeres scapularis
Invertivore
Centropyge multispinis
Invertivore
Novaculichthys taeniourus
Invertivore
Pomacanthus semicirculatus
Omnivore
Stethojulis albovittata
Invertivore
POMACENTRIDAE
Stethojulis balteata
Invertivore
Abudefduf sexfasciatus
Omnivore
Stethojulis bandanensis
Invertivore
Abudefduf sparoides
Omnivore
Thalassoma hebraicum
Invertivore
Abudefduf vaigiensis
Omnivore
Thalassoma lunare
Invertivore
Chrysiptera annulata
Planktivore
Chrysiptera unimaculata
Herbivore
LETHRINIDAE
Invertivore
Lethrinus harak
Invertivore
Chyrsiptera biocelleta
Omnivore
Lethrinus mahsena
Invertivore
Dascyllus aruanus
Omnivore
Lethrinus nebulosus
Invertivore
Dascyllus trimaculatus
Omnivore
Lethrinus sp.
Invertivore
Neopomacentrus sororius
Planktivore
Lethrinus variegatus
Invertivore
Plectroglyphidodon lacrymatus
Herbivore
32
Species
Trophic
group
SCARIDAE
Species
Trophic
group
SIGANIDAE
Chlorurus sordidus
Herbivore
Siganus sutor
Leptoscarus vaigiensis
Herbivore
TETRAODONTIDAE
Arothron immaculatus
33
Herbivore
Invertivore