Download South Coast Biodiversity Monitoring II-Final

KENYA COAST DEVELOPMENT
PROJECT
Natural Resource Management (Component 2)
KCDP South Coast Ecosystem Monitoring and Health Assessment Report:
Vanga-Shimoni-Funzi Bay Area
KMFRI Technical Report of the Monitoring conducted in December, 2014
Research geared towards promoting environmentally sustainable management of
Kenya’s coastal and marine resources
KCDP Technical Report, January 2015
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 (Shimoni), managers of community conserved,
areas, managers of Marine Parks,
Boat, diving and logistic support: KWS, KMFRI, and PILI PIPA Dive Centre
(Shimoni)
Report Writing and Data analysis: Charles Mitto Kosore, Boaz Ohowa,
Judith Okello, Jelvas Mwaura, Shaaban Mwachireya, Lilian Nduku, Victor
Mwakha, Linet Kiteresi, Charles Muthama, Veronica Wanjeri, Joel Gatagwu ,
Levy Otwoma, Jillo Katello, Julius Okondo, Michael Njoroge, Noah
Ng’isiange, Samuel Ndirangu, Joseph Kamau, Eric Okuku, Steve Mwangi.
For bibliographic purpose, this document should be cited as follows;
KMFRI, 2015. KCDP Monitoring seagrass beds and coral reefs of the South Coast of
Kenya: Research Geared towards Promoting Environmentally Sustainable
Management of Kenya’s Coastal and Marine Resources, KMFRI technical report
series, Mombasa.
For further information please contact:
The Director
Kenya Marine and Fisheries Reseach Institute
P.O. Box 81651 – 80100, MOMBASA, KENYA
Tel: 254-020-8021560/1, Fax: 254-020-2353226
Email: [email protected], Website: www.kmfri.co.ke
i
Table of contents
Acknowledgements .......................................................................................................................... i
Table of contents .............................................................................................................................. ii
List of figures .................................................................................................................................... iii
List of tables ...................................................................................................................................... iv
Abbreviations & Acronyms ......................................................................................................... iv
Executive summary ......................................................................................................................... v
1. Seagrass Ecosystem ............................................................................................................... 1
1.1 Abstract.................................................................................................................................... 2
1.2 Introduction ........................................................................................................................... 2
1.3 Methodology .......................................................................................................................... 3
1.3.1 Study sites ...................................................................................................................... 3
1.3.2 Seagrass habitat survey ............................................................................................ 3
1.3.3 Macrofaunal counts .................................................................................................... 3
1.3.4 Fish counts ..................................................................................................................... 3
1.4 Results ...................................................................................................................................... 4
1.4.1 Seagrass cover .............................................................................................................. 4
1.4.2 Seagrass species ........................................................................................................... 4
1.4.3 Algae cover ..................................................................................................................... 6
1.4.4 Shoot density ................................................................................................................. 6
1.4.5 Canopy height ............................................................................................................... 7
1.4.6 Invertebrate counts .................................................................................................... 7
1.4.7 Fish abundance and diversities ............................................................................. 9
1.4.8 Water quality.............................................................................................................. 10
1.4.9 Phytoplankton and Zooplankton ........................................................................ 13
1.5 Discussion ............................................................................................................................ 15
1.6 Conclusion ........................................................................................................................... 17
1.7 Recommendations ............................................................................................................ 17
1.8 References ........................................................................................................................... 17
2. Coral Reef Ecosystem......................................................................................................... 19
2.1 Introduction ........................................................................................................................ 20
2.2 Methodology ....................................................................................................................... 20
2.3 Results ................................................................................................................................... 21
2.3.1 Substrate (benthic) composition ........................................................................ 21
2.3.2 Coral Genera and Composition ........................................................................... 22
2.3.3 Fish Abundance and Composition ..................................................................... 22
2.3.4 Invertebrate abundance and Composition ..................................................... 24
2.3.5 Water Quality ............................................................................................................. 25
2.3.6 Phytoplankton and Zooplankton ........................................................................ 28
2.4 Discussion ............................................................................................................................ 30
2.5 Management recommendations and interventions ............................................ 32
2.6 References ........................................................................................................................... 33
ii
List of figures
Figure 1.1: Average cover of seagrasses observed in Kibuyuni, Wasini and Sii
Island during the three sampling sessions. .................................................................. 4
Figure 1.2: Average cover of seagrass species observed in Wasini during the
three sampling sessions. ...................................................................................................... 5
Figure 1.3: Average cover of seagrass species observed in Sii Island during the
three sampling sessions. ...................................................................................................... 5
Figure 1.4: Average cover of seagrass species observed in Kibuyuni site during
the three sampling sessions. .............................................................................................. 6
Figure 1.5: Average algae cover observed in Kibuyuni, Wasini and Sii Island
during the three sampling sessions................................................................................. 6
Figure 1.6: Average shoot densities of seagrasses observed in Kibuyuni, Wasini
and Sii Island during the three sampling sessions. ................................................... 7
Figure 1.7: Average canopy heights of seagrasses observed in Kibuyuni, Wasini
and Sii Island during the three sampling sessions. ................................................... 7
Figure 1.8: Densities of invertebrates observed in Kibuyuni, Wasini and Sii
Island during the three sampling sessions. .................................................................. 8
Figure 1.9: Densities of Tripneustes gratilla observed in Kibuyuni, Wasini and Sii
Island during the three sampling sessions. .................................................................. 8
Figure 1.10: Fish densities observed in Kibuyuni, Wasini and Sii Island during
the three sampling sessions. .............................................................................................. 9
Figure 1.11: Fish species observed in Kibuyuni, Wasini and Sii Island during the
three sampling sessions. ...................................................................................................... 9
Figure 1.12: Fish families observed in Kibuyuni, Wasini and Sii Island during the
three sampling sessions. ................................................................................................... 10
Figure 1.13: South Coast seagrass phytoplankton abundances ................................ 13
Figure 1.14: South Coast seagrass phytoplankton diversity indices....................... 13
Figure 1.15: South Coast seagrass phytoplankton group abundances................... 14
Figure 1.16: South Coast seagrass zooplankton abundances .................................... 14
Figure 1.17: South Coast seagrass zooplankton diversity indices ........................... 15
Figure 1.18: South Coast seagrass zooplankton group abundances ............................... 15
Figure 2.1: Substrate composition of Funzi-Shimoni-Vanga area over a three
year (2012/3/4) survey period ..................................................................................... 21
Figure 2.2: Substrate composition (%) of reef sites over a three year survey
period (2012-2014)............................................................................................................ 22
Figure 2.3: Coral genera by rank abundance. Two different abundance statistics
are shown, scaled from 1 (highest) to zero (lowest). The number of sites
shows genera present at all sites (p=1) to those present in only one site
(p>0), with a blue line and square symbols. The red line with diamonds
combines information on relative abundance of each genus at each site ..... 22
Figure 2.4: Fish abundance (#/250 m2) from study reefs of the Funzi-ShimoniVanga area .............................................................................................................................. 23
Figure 2.5: Number of fish (/250m2) from selected families observed in reef
sites of the Funzi-Shimoni-Vanga area. ...................................................................... 24
Figure 2.6: Abundance of selected invertebrates observed in the Shimoni reef
sites. .......................................................................................................................................... 24
Figure 2.7: Abundance (#/2502) of some important economically and
ecologically invertebrate from the Shimoni-Vanga area. .................................... 25
iii
Figure 2.8: South coast coral reef phytoplankton abundance. .................................. 28
Figure 2.9: South coast coral reef phytoplankton diversity indices ........................ 28
Figure 2.10: South Coast coral reef phytoplankton group abundances ................. 29
Figure 2.11: South Coast coral reef zooplankton abundances .................................. 29
Figure 2.12: South Coast coral reef zooplankton diversity indices ......................... 30
Figure 2.13: South Coast coral reef zooplankton group abundances ..................... 30
List of tables
Table 1.1: Concentrations of water quality parameters per site per date of
sampling in seagrass beds................................................................................................ 12
Table 1.2: Interaction between water quality and seagrass parameters .............. 12
Table 2.1: Concentrations of water quality parameters per site per date of
sampling in coral reef habitats ....................................................................................... 26
Abbreviations & Acronyms
BOD
CCA
E
H
KCDP
KMFRI
MPA
N
R.
RC
S
SA
SM
TSS
UNEP
Biological oxygen demand
Community Conservation Areas
Evenness
Species diversity index
Kenya Coast Development Programme
Kenya Marine And Fisheries Research Institute
Marine protected area
Abundance
River
Regeneration class
Richness
South Coast Assessment
South Coast Monitoring
Total suspended solids
United Nations Environment Programme
iv
Executive summary
With environmental and biodiversity baseline survey of the South Coast (Kwale
County) completed in 2012, subsequent monitoring of specific sites to determine
temporal and spatial changes in biodiversity was necessary. The assessment of the
status of these marine ecosystems and biodiversity is therefore a prerequisite in the
quest to identify and formulate strategic management options for conservation and the
optimal and sustainable utilization of these marine resources.
Seagrass cover, shoot densities, and canopy height of seagrasses generally varied
significantly with sites. There was however no particular trend in the changes
observed in the three sampling sessions. The study suggests the variations could be
attributed to influences ammonium, TSS, nitrates and suspended organic matter
concentrations. However, generally, invertebrate densities were observed to decrease.
The observed high densities of Tripneustes gratilla did not correspond to low seagrass
cover and this need to be further investigated in the next monitoring. Fish densities
and species diversities were also observed to vary across seagrass sites and across
sampling times. Generally, Kibuyuni was observed to exhibit highest densities and
diversities of fish species.
Mean coral cover in the study area was estimated to be around 31%, the lowest and
highest cover being measured in Kiromo (19.0%) and Wasini CCA (41%),
respectively. A total of one hundred and thirty seven (137) fish species belonging to
30 genera were observed in 2013 as opposed to 247 species from 29 genera in 2014
and 3 unidentified species also observed. Generally fish abundance in individual reef
sites did not differ significantly between years neither did fish family abundance
differ significantly between years but was lower in 2012 compared to other years. A
sharp increase in the ecological important sea urchin was observed in 2014 relative to
2013 as opposed to declining trend in the economic invertebrate species such as
bivalves, gastropods, mollusk and crabs.
Total Suspended Solids (TSS) is generally observed to be invariably distributed
among the sites; however, Sii Island seems to have higher concentrations, probably
due to the effects of wave action or discharge from river Umba. Low dissolved
oxygen was also recorded in December 2014 compared to the preceding years.
v
1. Seagrass Ecosystem
Authors: Mwakha V. A., Daudi L. N., Ndirangu S. G., Kimathi
A., Nzioka T., Muthama C., Mitto C.
1
1.1 Abstract
Seagrass meadows offer valuable ecosystem services, including fisheries, which are
beneficial to man for food security and income. However, seagrasses are subject to
frequent disturbance and overexploitation leading to their continued loss. The aim of
the current study was to monitor seagrass habitat characteristics and the fauna they
support. At each site, three permanent (50m long with 25m between transects)
transects were laid parallel to the shoreline and seagrass cover, shoot density and
canopy height quantified. Along the same transects, invertebrate counts were
conducted on either 2m. In addition, transects measuring 50 m length and 5 m width
were laid parallel to the shore with a distance of 20 m between transects. The
underwater visual census (UVC) technique was used to count fish encountered 2.5 m
on each side of the transect line. Seagrass cover, shoot densities, and canopy height of
seagrasses generally varied with site and across three sampling sessions. Water
quality parameters were observed to correlate positively with seagrass shoot density
and canopy height. Invertebrate densities were observed to decrease in densities with
lowest densities. Fish densities and species diversities were also observed to vary
across sites and across sampling times with Kibuyuni observed to exhibit highest
densities and diversities of fish species. Temporal monitoring of seagrass habitat
characteristics and the fauna they support is recommended to establish patterns and
for management and conservation of these important ecosystems.
1.2 Introduction
Seagrass ecosystems provide a myriad of valuable ecosystem goods and services that
are beneficial to man either directly or indirectly (Costanza et al., 1997). They are
important in nutrient cycling, sediment stabilization, and oxygenation of surrounding
water, erosion control, reduction of wave impacts, decreasing concentration of
suspended particles and carbon capture and storage (Costanza et al., 1997; Barbier et
al., 2011). Seagrass meadows also provide unique and aesthetic landscape that is
suitable for diverse flora and fauna thus enhancing opportunities for tourism,
recreation, education and research (Barbier et al., 2011). They also offer an indirect
cultural value to humans (de la Torre-Castro and Rönnbäck, 2004) and are connected
to adjacent coral reefs and mangroves supporting their productivity and biodiversity
(Unsworth et al., 2008).
Seagrass meadows directly support fisheries in developing countries (CullenUnsworth et al., 2014) supporting a major source of fish based food supply of
subsistance and commercial value (Unsworth et al., 2014). However, like many other
ecosystems, seagrass beds are under presure from multiple human activities and
degredation that may affect their productivity (Orth et al., 2006) hence their fast rate
of global decline (Waycot et al., 2009). Major drivers of loss include sedimentation,
eutrophication which interact with among others sea urchin overgrazing, vegetation
disturbances and climate change effects such as sea level rise (Orth et al., 2006; Eklof
et al., 2008). Conservation programmes do not recognise seagrass ecosystems
2
ecologic and economic values which excerbates their loss (Unsworth et al., 2010). In
the Western Indian Ocean (WIO) region, little is known about the links between
seagrass beds and the fauna they support (Unsworth et al., 2007). Hence, the aim of
this study was to monitor seagrass habitat characteristics and the fauna they support.
1.3 Methodology
1.3.1 Study sites
Three sites located in Kwale County on the southern part of the Kenyan coast were
sampled. The sites included Wasini Community Conservation Area (CCA), Sii Island
and Kibuyuni. Seagrass beds in all the sampled sites are continuous from the shallow
intertidal areas which are dominated by pioneer species to deeper areas where the
climax species dominate. All sites occur on non-protected areas where fisheries
activities are permitted but regulated on methods of gear including mesh sizes of nets,
amount, size, age and species or composition of species of fish caught (Fisheries Act,
2012). However, Kibuyuni and Wasini communities have established CCAs in 2010
and 2008 respectively that are controlled by beach management units (BMUs) and in
which all forms of extractive exploitation are not permitted (Maina et al., 2011). The
monitoring study was carried out at the beginning of December 2014.
1.3.2 Seagrass habitat survey
At each site, three permanent (50m long with 25m between transects) transects were
laid parallel to the shoreline and seagrass cover, shoot density and canopy height
quantified. At each site, three transects were laid within which the triplicate
parameters were recorded after a distance of every 20 m.
Seagrass cover, shoot density and canopy height were determined using standard
quadrats for each parameter as described in the SeagrassNet protocol (Short and
Coles, 2001) in order to capture the zonation patterns of seagrass. Species
identification was done to the lowest taxonomic level
1.3.3 Macrofaunal counts
Along the same transects as the ones in which seagrass habitat characteristics were
established, macrofaunal counts were conducted 2m on either side of the transect
(Short and Coles, 2001).
1.3.4 Fish counts
At each site, six visual transects were conducted. Sampling was conducted using the
underwater visual census (UVC) method with snorkeling equipment (English et al.,
1997). 50 m belt transects were laid parallel to the beach and fish counted in an area
of 2.5 m on either side of the transect tape hence a total of 250 m2. Fish species
identification was done to the lowest taxonomic level according to Lieske and Myers
(2002) and Froese and Pauly (2015).
3
1.4 Results
1.4.1 Seagrass cover
There were varying trends in seagrass cover across the sites monitored (Fig.1.1). In
Wasini site for instance, seagrass cover reduced in March 2014, then increased to
67% in December 2014. In Kibuyuni and Sii island sites, the trend was different as
seagrass cover was highest during the second sampling.
Figure 1.1: Average cover of seagrasses observed in Kibuyuni, Wasini and Sii Island during the three
sampling sessions.
1.4.2 Seagrass species
Eight species of seagrass were observed in Wasini, dominated by Enhalus acoroides
and Halodule uninervis (Fig. 1.2). There were increasing trends in H. uninervis and
Cymodocea rotundata and decreasing in E. acoroides and Cymodocea serrulata. A
total of six species were observed in Sii island (Fig. 1.3) dominated by H. uninervis.
Increasing trends in cover of E. acoroides was observed although not significant.
Seven species of seagrass were observed in Kibuyuni dominated by Thalassodendron
ciliatum (Fig. 1.4). Seagrass species cover varied during each sampling session.
4
Figure 1.2: Average cover of seagrass species observed in Wasini during the three sampling sessions.
Figure 1.3: Average cover of seagrass species observed in Sii Island during the three sampling
sessions.
5
Figure 1.4: Average cover of seagrass species observed in Kibuyuni site during the three sampling
sessions.
1.4.3 Algae cover
The algae cover in Wasini was highest during the first monitoring then decreased
substantially during the following sampling. Algae cover decreased progressively in
Kibuyuni while there was a gradual increase in algae cover in Sii Island (Fig. 1.5).
Figure 1.5: Average algae cover observed in Kibuyuni, Wasini and Sii Island during the three
sampling sessions.
1.4.4 Shoot density
Seagrass shoot densities were relatively constant in Wasini and Kibuyuni, but
increased in Sii Island in March 2014 (Fig. 1.6).
6
Figure 1.6: Average shoot densities of seagrasses observed in Kibuyuni, Wasini and Sii Island during
the three sampling sessions.
1.4.5 Canopy height
There were varying trends in canopy heights of seagrasses across the sites monitored
(Fig. 1.7). In Wasini site, there was a significant decrease in March 2014 followed by
an increase in average height in December 2014.
Figure 1.7: Average canopy heights of seagrasses observed in Kibuyuni, Wasini and Sii Island during
the three sampling sessions.
1.4.6 Invertebrate counts
There was a general decrease in invertebrate densities in all the sites monitored (See
Fig. 1.8 below).
7
Figure 1.8: Densities of invertebrates observed in Kibuyuni, Wasini and Sii Island during the three
sampling sessions.
Densities of Tripneustes gratilla were highest in December 2012 in Wasini and
Kibuyuni. No T. gratilla were observed in Wasini in March 2014, but there was a
significant increase in the following sampling (Fig. 1.9). Generally, in March 2014,
there was a decrease in T. gratilla densities in Wasini and Kibuyuni. No T. gratilla
were observed in Sii Island.
Figure 1.9: Densities of Tripneustes gratilla observed in Kibuyuni, Wasini and Sii Island during the
three sampling sessions.
8
1.4.7 Fish abundance and diversities
1.4.7.1 Fish densities
Figure 1.10: Fish densities observed in Kibuyuni, Wasini and Sii Island during the three sampling
sessions.
There were varying trends in fish densities in all the sites (Fig. 1.10). Highest
densities of fish were observed in Kibuyuni. There was a small increase in fish
densities in Kibuyuni in March 2014 and a significant decrease in December 2014. In
Wasini on the contrary, there was a significant decrease in densities in March 2014,
and a slight increase in December 2014. A gradual increase in fish densities was
observed in Sii Island in March 2014, then a significant increase in December 2014.
1.4.7.2 Fish species diversities
Figure 1.11: Fish species observed in Kibuyuni, Wasini and Sii Island during the three sampling
sessions.
9
A total of 99 species were observed, which varied across sites and sampling times.
The highest density of fish species was observed in Kibuyuni in March 2014 (Fig.
1.11). There was a decrease in fish species in March 2014 and an increase in
December 2014 in Wasini and Sii Island. In Kibuyuni however, there was a
significant increase in fish species densities in March 2014, and a decrease in
December 2014.
1.4.7.3 Fish families
A total of 28 fish families were observed with the major ones being of the families
Apogonidae, Labridae, Lethrinidae, Lutjanidae, Pomacentridae, Scaridae and
Siganidae.
Figure 1.12: Fish families observed in Kibuyuni, Wasini and Sii Island during the three sampling
sessions.
There were varying trends in fish families in all the sites (see Fig. 1.12 above). In
Kibuyuni for instance, the highest number of fish families were observed in March
2014. In Wasini Island, there were 11 families in December 2012, 9 in March 2014
and 13 in December 2014. Sii Island had the lowest numbers of fish families
observed.
1.4.8 Water quality
Nutrients’ dynamics were also observed in the seagrass beds (Table 1.1). December
2012 recorded high concentrations of phosphate while higher concentrations of
nitrates and ammonium were observed in December 2014. Kibuyuni recorded the
highest concentrations of phosphates and nitrates throughout the monitoring dates.
Highest concentrations of ammonium were recorded in Wasini Tengefu followed by
Sii Island and lowest in Kibuyuni. Chlorophyll-a, was not measured in December
2012; however, high concentrations are recorded in March 2014 but reduced in
December 2014. Dissolved oxygen was not measured in December 2012, but low
10
concentrations were recorded in December 2014 compared to March 2014. This may
have been attributed to the high concentration of suspended organic matter, which led
to high demand for oxygen to break down as indicated by the high concentrations of
BOD. Concentrations of Total Suspended Solids (TSS) are higher in March 2014,
compared to the other sampling dates. However, the concentrations were generally
invariably distributed among the sites, except in December 2014 where variability is
noticed. There was a significant positive relationship between seagrass shoot density
and ammonium, TSS and suspended organic matter (Table 1.2). There was also a
significant positive relationship between seagrass canopy height, nitrate and TSS
concentration and a negative relationship between canopy height and ammonium
concentrations.
11
Table 1.1: Concentrations of water quality parameters per site per date of sampling in seagrass beds.
DATE
STN
December
2012
Wasini
Tengefu
Kibuyuni
Sii
Island
March
Wasini
2014
Tengefu
Kibuyuni
Sii
Island
December Wasini
2014
Tengefu
Kibuyuni
Sii
Island
Phosphates
(mg/L)
Nitrate
( mg/L)
Ammonium D.O
(mg/L)
(mg/L)
BOD
(mg/L)
TSS(mg/l) Suspended
organic matter
(mg/l)
Chl-a (ug/l)
0.03±0.01
0.15
0.002±0.001
0.002±0.001
0.044±0.017
0.013±0.005
-
-
35.7±14.8
27.0±0.5
5.1±1.0
3.3±1.7
-
0.03
0.001
0.05±0.03
-
-
32.1±12.6
5.5±4.0
-
0.03
0.003±0.001
0.030±0.004 0.008±0.003
0.007±0.002
0.004±0.003
6.54±0.04 3.28
35.0±2.8
6.4
3.32±0.06 36.0
5.5±1.3
5.5±0.7
0.33±0.16
0.44±0.23
0.021±0.006 0.003±0.002
0.008±0.004
5.3±0.5
8.0±1.4
0.36±0.11
0.03±0.01
0.04±0.01
0.005±0.001
0.010±0.005
0.06±0.03
0.06±0.01
4.48±0.15 4.16±0.51 28.7±4.0
4.0±0.1
4.4±0.1
27.0±3.6
12.7±2.5
9.7±1.5
0.06±0.01
0.05±0.01
0.04±0.01
0.005±0.001
0.06±0.02
4.5±0.4
6.7±0.6
0.05±0.01
Table 1.2: Interaction between water quality and seagrass parameters
Phosphates
(mg/L)
Nitrate (
mg/L)
Ammonium
(mg/L)
TSS(mg/l)
SPOM
(mg/l)
Shoot
2,8845E-15 0,601209466 4,67276E-13 3,16575E-11 2,39695E-09
density
Canopy
0,14567329 0,003441347 0,025974511 0,000930024 0,792349174
Height
12
2.88±0.49 34.5±3.5
4.13±0.52 31.3±7.4
1.4.9 Phytoplankton and Zooplankton
Within the seagrass habitat, the phytoplankton abundances declined over time with a
drastic increase in December 2014 within the Wasini Jetty area in which restoration
activities were taking place (Fig. 1.13)
Figure 1.13: South Coast seagrass phytoplankton abundances
Phytoplankton diversity within the seagrass habitat had no significant variation in its
species diversity and evenness unlike the species richness that increased with time
during the monitoring period (Fig. 1.14).
Figure 1.14: South Coast seagrass phytoplankton diversity indices
The phytoplankton groups within the seagrass habitat decreased varied significantly
with most group abundance recorded in March 2014. The diatoms were the most
13
abundant group during the monitoring period followed by the dinoflagellates and
cyanobacteria (Fig. 1.15).
Figure 1.15: South Coast seagrass phytoplankton group abundances
There was a steady increase in zooplankton abundance over time during the
monitoring period within the seagrass habitat (Fig. 1.16).
Figure 1.16: South Coast seagrass zooplankton abundances
Within the seagrass habitat, there was insignificant variation in species diversity,
evenness and richness during the monitoring period but the species richness decreased
during the February 2015 monitoring campaign (Fig. 1.17).
14
Figure 1.17: South Coast seagrass zooplankton diversity indices
The seagrass zooplankton group abundances were most with the fish eggs within the
Wasini Jetty area in which restoration activities had been taking place (Fig. 1.18).
Figure 1.18: South Coast seagrass zooplankton group abundances
1.5 Discussion
Seagrass cover, shoot densities, and canopy height of seagrasses generally varied
significantly with site. In Wasini site for instance, seagrass cover reduced in March
2014, then increased to 67% in December 2014. The increase in cover could be
attributed to enhanced awareness of seagrass importance. Hence local communities
are increasingly involved in seagrass conservation efforts including restoration of
degraded areas. In Kibuyuni and Sii island sites on the other hand, the trend was
different as seagrass cover was highest during the second sampling exercise. The
trend in Kibuyuni could be attributed to the ongoing seaweed farming in the
monitoring site, although algae cover was observed to continuously decrease.
Generally seaweed farming has been observed to lead to a decrease in cover of
seagrass beds elsewhere (Eklöf et al., 2006). The seagrass shoot densities were
15
relatively constant in Wasini and Kibuyuni, but were observed to increase in Sii
Island in March 2014. This could be associated with sedimentation in Sii Island
leading to increase in densities of pioneer species e.g. Halodule species and Halophila
ovalis. Hence, the observed varying trends in seagrass canopy heights could be
associated with dynamics in densities of climax and pioneer species. A significant
positive relationship was observed between seagrass shoot density and ammonium,
TSS and suspended organic matter implying they could be influencing seagrass shoot
density. On the other hand, a significant positive relationship observed between
seagrass canopy height and nitrate and TSS concentration could imply that these
nutrients have a positive influence on seagrass height. The negative relationship
observed between canopy height and ammonium concentrations could suggest that an
increase in ammonium concentration had a negative influence on seagrass height.
However, these findings need to be investigated further.
Invertebrate densities were observed to decrease in densities with lowest densities
observed in December 2014. Of particular importance is Tripneustes gratilla because
of their related effects on seagrass assemblage dynamics. Although their predators
were not observed during the study, explosions in their densities has been associated
with overfishing of their predators leading to overgrazing of entire seagrass beds
(Eklöf et al., 2008).
Highest densities of this sea urchin were observed in Kibuyuni and Wasini in
December 2012 although this did not correspond to a reduction in cover. Further
investigations on their populations in relation to seagrass cover are therefore
recommended. Varying trends in fish densities and species diversities were observed
across sites. In all sampling durations, highest fish species diversities were observed
in Kibuyuni while fish densities were highest in December 2012 and March 2014 in
Kibuyuni and in December 2014 in Sii Island. The high fish species diversities and
densities could be attributed to the fact that Kibuyuni is a community conserved area
(CCA). Protected areas are expected to exhibit higher fish species abundances and
richness than unprotected ones (McClanahan, 1994). Surprisingly however, fish
densities Wasini CCA were high in December 2012, but decreased during the
subsequent monitoring. This could be attributed to poor enforcement of CCA
regulations, among other factors, although this needs further investigation.
Nonetheless, densities of fish species increased in December 2014. This could be
associated with the ongoing coral restoration in the CCA leading to spill over of fish
to the adjacent seagrass beds. Generally, Sii Island is an open access area hence
subjected to fishing activities including fishing using destructive fishing gear such as
beach seines. Destructive fishing activities such as beach seining are known to
degrade seagrass beds and capture high numbers of juvenile fish resulting to decline
in fish species diversity and abundance (Mangi and Roberts, 2007). This could
explain the low diversities and densities of fish species observed at Sii island in the
first two sampling sessions. In fact, during the first sampling excercise, beach seining
activity was observed at Sii island. Regardless, it is expected that removal of such
activity will lead to recovery of fish species assambleges eventually hence increased
16
fish species densities and richness as has been observed in other areas of the Kenyan
coast (McClanahan and Mangi, 2001). Major fish families characterising seagrass
beds were observed, but there were varying trends in fish families observed across all
sites. Generally, fish families increased in Kibuyuni in March 2014 but declined in
Wasini and Sii Island. It is recommended that fish species assemblages be monitored
seasonally to understand their dynamics in relation to seagrass habitat characteristics.
1.6 Conclusion
Seagrass cover, shoot densities, and canopy height of seagrasses generally varied
significantly with site. There was however no particular trend in these parameters in
the three sampling sessions although the study suggests they could have been
influenced by ammonium, TSS, nitrates and suspended organic matter concentrations.
However, generally, invertebrate densities were observed to decrease in densities. The
observed high densities of Tripneustes gratilla did not correspond to low seagrass
cover. Fish densities and species diversities were also observed to vary across sites
and across sampling times. Generally, Kibuyuni was observed to exhibit highest
densities and diversities of fish species.
1.7 Recommendations
Further investigations on populations of macrofauna, particularly Tripneustes gratilla
in relation to seagrass cover are recommended. There is need to relate water quality
parameters with seagrasses to understand their influence on seagrasses. In addition,
fish species assemblages need to be monitored seasonally and regularly to understand
their dynamics in relation to seagrass habitat characteristics. Fishing activities across
sampling sites should also be monitored.
1.8 References
Barbier, E. B., Hacker, S. D., Kennedy, C., Koch, E.W., Stier, A. C., Silliman, B. R.,
2011. The value of estuarine and coastal ecosystem services. Ecol. Monogr.
81, 169-193.
Costanza, R., d’Arge, R., De Groot, R., Farber, S., Grasso, M., Hannon, B., Naeem,
S., Limburg, K., Paruelo, J., O’Neill, R. V., Raskin, R., Sutton, P., van den
Belt, M., 1997. The value of the world’s ecosystem services and natural
capital. Nature 287, 253-260.
Cullen-Unsworth, L. C., Mtwana, N. L., Paddock, J., Baker, S., McKenzie, L. J.,
Unsworth, R. K. F., 2014. Seagrass meadows globally as a coupled social–
ecological system: Implications for human wellbeing. Mar. Pollut. Bull. 83,
387–397.
de la Torre-Castro, M., Ronnback, P., 2004. Links between humans and seagrasses –
an example from tropical East Africa. Ocean Coast. Manag. 47 (7–8), 361–
387.
Eklöf, J. S., Henriksson, R., Kautsky, N., 2006. Effects of tropical open-water
seaweed farming on seagrass ecosystem structure and function. Marine
Ecology Progress Series; 325:73–84.
17
Eklöf, J, M., Delatorrecastro, Gullstrom, M., Uku, J., Muthiga, N., Lyimo, T.,
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.
Froese, R., Pauly, D. Editors., 2015. FishBase. World Wide Web electronic
publication. www.fishbase.org, version (02/2015).
Lieske, E., Myers, R., 2002. Coral Reef Fishes: Indo-Pacific and Caribbean (Revised).
Princeton University Press, 400pp.
Maina, G. W., Osuka, K., Samoilys, M., 2011. Opportunities and challenges of
Community-based protected areas in Kenya. CORDIO status report.
Mangi, S. C., Roberts, C. M., 2007. Factors influencing fish catch levels on Kenya’s
coral reefs. Fisheries Management and Ecology, 14, 245-253.
McClanahan, T. R., Nugues M., Mwachireya, S., 1994. Fish and sea urchin herbivory
and competition in Kenyan coral reef lagoons: the role of reef management.
Journal of Experimental Marine Biology and Ecology 184, 237-254.
McClanahan, T. R., Mangi, S., 2001. The effect of a closed area and beach seine
exclusion on coral reef fish catches. Fisheries Management and Ecology,
8: 107–121.
Orth, R. J., Carruthers. T. J.B., Dennison, W. C., Duarte, C. M., Fourqurean, J. W.,
Heck, K. L., et al., 2006. A global crisis for seagrass ecosystems. Bioscience;
56:987-96.
Short, F.T., Coles, R. G. (eds.), 2001. Global Seagrass Research Methods. Elsevier
Science B.V., Amsterdam. 473 pp.
Unsworth, R. K. F., De Grave, S., Jompa, J., Smith, D. J., Bell, J. J., 2007a. Faunal
relationships with seagrass habitat structure: a case study using shrimp from
the Indo-Pacific. Marine and Freshwater Research, 58, 1008–1018.
Unsworth, R. K. F., De León, P. S., Garrard, S. L., Jompa, J., Smith, D. J., Bell, J. J.
2008. High connectivity of Indo-Pacific seagrass fish assemblages with
mangrove and coral reef habitats. Marine Ecology Progress Series 353: 213–
224.
Unsworth, R. K. F., Cullen, L. C., Pretty, J. N., Smith, D. J., Bell, J. J., 2010.
Economic and subsistence values of the standing stocks of seagrass fisheries:
potential benefits of no-fishing marine protected area management. Ocean.
Coast. Manag. 53, 218-224.
Unsworth, R. K. F., Hinder, S., Bodger, O. G., Cullen-Unsworth, L. C., 2014. Food
supply depends on seagrass meadows in the coral triangle. Environ. Res. Lett.
9
Waycott, M., Duarte, C. M., Carruthers, T. J. B., Orth, R. J, Dennison, W. C., et al.,
2009. Accelerating loss of seagrasses across the globe threatens coastal
ecosystems. Proceedings of the National Academy of Science USA 106:
12377–12381.
18
2. Coral Reef Ecosystem
Authors: Mwachireya S. A., Mwaura J., Kilonzo J. and
Ndirangu S. G.
19
2.1 Introduction
The Funzi-Shimoni-Vanga marine area of the southern Kenya coast covers an area of
~150 km2 is characterized by an intricate network of estuarine creeks fringed with
highly productive mangrove forests. It is also endowed with other abundant and
diverse marine resources and is considered among the richest marine ecosystems in
Kenya alongside the Lamu Achipelago, Ungwana Bay and the North Kenya and
Malindi Banks. In the nearshore areas, fringing and patch coral reefs and seagrass
beds dominate, exhibiting high biodiversity and productivity. Shirazi Creek in Funzi
Bay has no permanent direct link to freshwater input but is influenced by River
Ramisi and sustained by groundwater seepage. The Shimoni-Vanga complex receives
freshwater discharge from Rivers Umba and Mwena via estuarine creeks and opens
out and experiences water exchange with the coral lagoons between Wasini and the
Kisite-Mpunguti barrier islands.
This is an important marine area in supporting local community livelihoods through
provision of nutrition and income harvesting. This area supports a thriving tourism
sector and inshore artisanal fishery within the coral reef and sea grass areas. These
critical systems are inter-linked through exchange of water, nutrients and sediments
by the tidally controlled circulation and river discharge (UNEP, 1998). However,
these ecosystems are under threat from land-based pollution associated with
agriculture and population growth, overharvesting and destructive forms of resource
exploitation leading to decline in fish catches, habitat modification and degradation
and the proliferation of undesirable organisms. For effective mitigation measures to
ensure sustainable exploitation of these marine ecosystems and their biodiversity
there is need to make deliberate efforts to understand the status of these resources and
the impacts and trends of the drivers of change. The assessment of the status of these
marine ecosystems and biodiversity is therefore a prerequisite in the quest to identify
and formulate strategic management options for conservation and the optimal and
sustainable utilization of these marine resources. Here we report the results of coral
reef biodiversity assessment and monitoring undertaken over a three year period
(2012-2014).
2.2 Methodology
Coral reef biodiversity surveys focused on three ecologically or economically
important components of the coral reefs: benthic cover and composition, fish and
macro-invertebrate abundance and composition and coral diversity (McClanahan et
al., 1999). Underwater Visual Census (UVC) was used to assess coral diversity and
benthic composition, fish and macro-invertebrates diversity and abundance. Number
of coral and fish taxa was used as the metric of biodiversity
Benthic cover and coral community composition at each reef was assessed using
transects and digital still photographs taken consistently from a height of 0.6-0.7
meters above the substratum. Three (3) photographs were randomly taken after every
10 m along a 50 m transect line and presence and percentage cover of the different
benthic types and coral cover determined using Coral Point Count estimate (CPCe)
20
software (McClanahan and Shafir, 1990). The benthic cover types were recorded as:
hard coral (HC), soft coral (SC), algal turf (AT), crustose coralline algae (CCA), sand
(S), sponge (SP), seagrass (SG), rubbles (R), coralline algae (CA) and macro algae
(MA) or fleshy algae (FA).
Coral diversity and abundance were recorded within a 50m x 2m belt transect, and
corals identified to genus level but where immediate identification was difficult, a
digital photograph of the coral was taken for later verification/identification using
field guide books (Veron, 2000; Wallace, 1999 and Sheppard and Obura, 2004). Fish
and macroinvertebrate surveys were carried out using 50m x 5m belt transects
following modification of commonly used sampling techniques (Allen 2005;
Samoilys and Randriamanantsoa, 2011). Fish and invertebrates were counted and
identified to species level where possible.
2.3 Results
2.3.1 Substrate (benthic) composition
Little differences were observed on substrate categories between years though 2014
was observed to have lower hard coral and high seagrass cover compared to previous
years i.e. 2012 and 2013 (Fig. 2.1). High cover of turf and fleshy algae that are
competitors for corals was measured compared to coralline algae over the 3 year
period. However, unlike turf and fleshy algae, coralline algae cover increased over
time, similar to sand, sponge and seagrass.
Figure 2.1: Substrate composition of Funzi-Shimoni-Vanga area over a three year (2012/3/4) survey
period
Mean coral cover in the study area was estimated to be around 31%, the lowest and
highest cover being measured in Kiromo (19.0%) and Wasini CCA (41%),
respectively (Fig. 2.2). Generally macroalgae or fleshy algae cover was high on all
sites except Wasini CCA and Kibuyuni reefs, however algal turf cover in all reef sites
was high ( > 15%). Kibuyuni reef exhibited higher sand, seagrass and rubble cover
relative to all other reefs. Highest sand cover was measured in Wasini CCA.
21
Figure 2.2: Substrate composition (%) of reef sites over a three year survey period (2012-2014).
2.3.2 Coral Genera and Composition
A total of fifty five (55) coral genera were observed in the study area, the highest and
lowest diversity being measured in Kibuyuni (40 genera) and Mwarembo (28),
respectively. Ten (10) coral genera were present at every site, and 35 (comprising
75% of genera recorded) were found at > 70% of sites. Reefs with high coral cover
also showed high coral diversity, although some sites exhibited a contrasting trend of
higher species richness with reduced coral cover (Sii Island, Kiromo), indicating that
community structure was dominated by few coral genera. Porites and Acropora were
the dominant genera whereas Pectinia, Plesiastrea and Tubastrea were observed
occasionally. The relative abundance curve (Fig. 2.3) shows that coral communities
are relatively homogenous, with the steep descent toward the end of the line
indicating rare genera. Wasini and Kibuyuni reefs had lower coral cover compared
to fully protected reefs and higher relative to other exploited reefs but with higher
diversity than reserves.
Relative Abundance of Genera
1.0
No. of sites
Relative Abundance
Relative Abundance
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Porites
Acropora
Galaxea
Platygyra
Favites
Favia
Fungia
Pocillopora
Montipora
Echinophyllia
Astreopora
Coscinaraea
Seriatopora
Echinopora
Pavona
Lobophyllia
Goniastrea
Hydnophora
Goniopora
Alveopora
Psammocora
Acanthastrea
Merullina
Isopora
Leptoseris
Tubinaria
Herpolitha
leptoria
Tubipora
Podabacea
pachyseris
stylophora
Cyphastrea
Diploastrea
Symphillia
Heliopora
Leptastrea
Gardineroseris
Montastrea
Physogyra
Plerogyra
ctenactics
Millepora
Cycloseris
Blastomussa
caulastrea
Gyrosmilia
Halomitra
Mycedium
Horastrea
Oxypora
Trachyphyllia
Oulophyllia
Pectinia
Plesiastrea
Tubastrea
0.0
Figure 2.3: Coral genera by rank abundance. Two different abundance statistics are shown, scaled
from 1 (highest) to zero (lowest). The number of sites shows genera present at all sites (p=1) to those
present in only one site (p>0), with a blue line and square symbols. The red line with diamonds
combines information on relative abundance of each genus at each site
2.3.3 Fish Abundance and Composition
Overall, two hundred and sixty two (262) species of fish belonging to 47 families and
112 genera with 3 unidentified species were observed during the surveys. A total of
22
one hundred and thirty seven (137) fish species belonging to 30 genera were observed
in 2013 as opposed to 247 species from 29 genera in 2014 (see Appendix 1). In 2012,
one hundred and thirty seven (137) species belonging to 29 families were observed. In
all surveys, Kiromo site exhibited the highest fish abundance (#/250m2) compared to
the rest of the study reefs. Generally fish abundance in individual reef sites did not
differ significantly between years neither did fish family abundance differ
significantly between years but was lower in 2012 compared to other years. Three (3)
families, Lutjanidae (emperors), Pempheridae (sweepers) and Pomacentridae
(damselfishes) dominated fish population in the study area, however there was a
significant decline in the abundance of Lethrinidae (snappers) and Blenniidae
(blennies) between 2013 and 2014 (14.7 to 3.80 individuals/250m2) though
Lutjanidae (emperors) increased within the same time period. Two species, the
damselfish Pomacentrus pavo and the snapper, Lutjanus russelli
Ecologically or economically important fish families such as Balistidae (triggerfish)
and Serranidae (rock cods) were very rare or absent altogether. Fish abundance was
highest in the Marine Park (no-take zones) with Kisite recording the highest density
and species richness. Within the Marine Reserve, Mpunguti Upper exhibited higher
fish densities than Mpunguti Lower. In the CCA, fish densities had the following
trends; Wasini Tengefu > Mwarembo > Kibuyuni. Lowest fish densities were
recorded in fully open access area. A sharp increase in fish density was observed in
Wasini CCA between 2012 and 2013 (Fig. 2.4). There was also a gradual increase and
decrease in fish abundance with time in Wasini CCA and Kibuyuni, respectively.
Figure 2.4: Fish abundance (#/250 m2) from study reefs of the Funzi-Shimoni-Vanga area
The most abundant species of all was the damselfish Neopomacentrus azysron at 56
and 100 individuals/250m2 in 2013 and 2014, respectively (Fig. 2.5). Other important
species in terms of numbers included Chromis dimidiata, C. viridis, Lutjanus
fluviflama and L. ruselli (>20 individuals/250m2).
23
Figure 2.5: Number of fish (/250m2) from selected families observed in reef sites of the FunziShimoni-Vanga area.
2.3.4 Invertebrate abundance and Composition
Number of invertebrates increased between 2013 and 2014 in all studied reef sites.
Fifty one (51) species of invertebrates were observed in 2013 compared to 27 in 2014
(Fig. 2.6). In 2013 invertebrates population was dominated by D. molle , S. notanda
and K. fascigera while in 2014, D setosum (128 individuals/250m2 but as high as 350
individuals/250m2 in Kibuyuni), K. humilis and D. molle dominated Unlike in many
exploited reefs, sea urchin abundance was low in 2013, the most populous urchin
being Diadema setosum (4.9 individuals/250m2). Overall, Kiromo reef exhibited the
lowest total abundance of invertebrates and Kibuyuni reef the highest as well as
greatest percentage increase.
Figure 2.6: Abundance of selected invertebrates observed in the Shimoni reef sites.
24
A sharp increase in the ecological important sea urchin was observed in 2014 relative
to 2013 as opposed to declining trend in the economic invertebrate species such as
bivalves, gastropods, mollusk and crabs (Fig. 2.7).
Figure 2.7: Abundance (#/2502) of some important economically and ecologically invertebrate from
the Shimoni-Vanga area.
2.3.5 Water Quality
Table 2.1 shows the concentrations of water quality parameters per site per date of
sampling. Nutrients generally tend to display their dynamics nature among the sites
studied per sampling date within coral reef habitats, where phosphate records higher
concentrations in December 2012, nitrate in March 2014 and ammonium in December
2014 respectively. Higher Chlorophyll-a concentrations are observed in March 2014.
These trends could be attributed to environmental conditions during the sampling
periods. Total Suspended Solids (TSS) is generally observed to be invariably
distributed among the sites; however, Sii Island seems to have higher concentrations,
probably due to the effects of wave action or discharge from river Umba. Low
dissolved oxygen is recorded in December 2014 compared to the preceding years.
This may have been attributed to the high concentrations of suspended organic matter,
which led to high demand for oxygen to break down as indicated by the high
concentrations of BOD.
25
Table 2.1: Concentrations of water quality parameters per site per date of sampling in coral reef habitats
DATE
STN
Phosphates
(mg/L)
Nitrates
(mg/L)
Ammonium
(mg/L)
D.O
(mg/L)
BOD
(mg/L)
TSS
(mg/l)
Suspended
organic
matter (mg/l)
Chl-a
(ug/l)
December
2012
Wasini
Tengefu
Kibuyuni
Sii Island
Mwarembo
Mwazaro
kiromo
Wasini
Tengefu
Kibuyuni
0.33±0.10
0.003±0.001
0.015±0.003
-
-
23.5
4
-
0.154±001
0.37±0.10
0.47±0.10
0.50±0.06
0.041±0.001
0.002±0.001
0.004
0.003
0.003
0.019±0.001
0.013±0.004
0.021±0.003
0.021±0.001
0.018±0.006
0.002±0.001
4.96
2.16
25
33.9
25.3
24±3
6.5
5.1
2.6
6.5±0.7
0.049±0.005
0.04±0.01
0.001
5.6
3.2
30
5
Sii Island
0.033±0.002
0.024±0.005
0.003±0.001
0.020±0.003
0.031±0.004
0.01
30.5±
5.0
28±1
Mwazaro
0.04±0.01
0.028±0.012
0.009±0.003
3.04±0.1
1
3.96±0.0
5
3.4±0.1
7.5±0.7
Mwarembo
0.028±0.007
0.022±0.003
0.0160.004
31.5±
6.0
29±3
10.5±2.1
Kiromo
5.48±0.0
5
6.36±0.0
5
6.36±0.0
5
6.6±0.1
Wasini
Tengefu
0.019±0.004
0.005±0.001
0.051±0.039
4.18±0.1
4
3.4±0.2
23.5±
2.1
11.5±2.1
0.33±0.1
1
0.26±0.0
3
1.02±0.2
5
0.31±0.0
8
0.34±0.2
1
1.19±0.5
3
0.07
March
2014
December
2014
26
3.44
6
7.5±0.5
Kibuyuni
0.028±0.004
0.006
0.035±0.004
3.6±0.1
Sii Island
0.026±0.002
0.006±0.002
0.023±0.013
Mwarembo
0.029±0.003
0.006±0.001
0.045±0.017
4.18±0.2
5
4.7±0.1
Mwazaro
0.032±0.002
0.006
0.044±0.001
4.7±0.1
Kiromo
0.032±0.001
0.005
0.035±0.015
4.7±0.2
27
4.08±0.2
3
4.48±0.6
8
4.36±0.0
6
4.36±0.4
0
4.36±0.6
8
30±9
12
0.04
38.5±
16.3
28±4
11±3
28±6
11±3
28±7
9.5±0.7
0.05±0.0
1
0.06±0.0
1
0.06±0.0
1
0.06±0.0
1
11
2.3.6 Phytoplankton and Zooplankton
Plankton monitoring activities of the Kenya South coast oceanic waters of took place
in December 2014 within the coral reef and Seagrass habitat. The phytoplankton
abundance showed an increase with time within the coral habitat in which restoration
activities had been taking place (Fig. 2.8).
Figure 2.8: South coast coral reef phytoplankton abundance.
Furthermore, the phytoplankton community composition showed an increase in
species richness with time within the coral reef habitat even though the phytoplankton
species diversity and evenness varied over the period of monitoring (Fig. 2.9).
Figure 2.9: South coast coral reef phytoplankton diversity indices
The coral reef habitat phytoplankton group abundances similarly showed an increase
as the monitoring and restoration programme continued with a drastic decrease in
Wasini Tengefu area for most of the phytoplankton groups (Fig. 2.10).
28
Figure 2.10: South Coast coral reef phytoplankton group abundances
Zooplankton abundance increased significantly with slight variations during the
monitoring period but showed an increase in December 2014 within the coral reef
habitat as seen in Fig. 2.11.
Figure 2.11: South Coast coral reef zooplankton abundances
Within the coral reef habitat, the zooplankton diversity varied significantly as seen
with the three indices that were of interest during the monitoring period namely the
species diversity, evenness and richness (Fig. 2.12).
29
Figure 2.12: South Coast coral reef zooplankton diversity indices
The zooplankton within the coral reef habitat were grouped as fish eggs, fish larvae
and others (encompassing all the taxa identified within the monitoring period). The
zooplankton increased as the monitoring continued but showed a marked increase in
December 2014 especially in Mwarembo site (Fig. 2.13).
Figure 2.13: South Coast coral reef zooplankton group abundances
2.4 Discussion
Substrate and coral composition, fish and macro-invertebrates observed in these
surveys raises two important issues of concern: habitat degradation and
overharvesting. The observed differences in status of biodiversity in heavily exploited
and community conserved reef sites over the monitoring period suggest recovery
potential of protected reefs through reduced levels of fishing, resulting in increased
coral cover and fish abundance in the community conserved areas. This is an
important development in view of the rapid population growth and scarcity of
livelihood alternatives in the area, and predicted increases in the frequency of coral
bleaching incidences, a combination of factors that could lead to further degradation,
30
resource depletion and the emergence of conflicts between resource users. The
presence of high coral cover in Kiromo suggests favorable habitat conditions despite
the presence of disturbances. It is thus important to target this reef for future
conservation, and serve, as refuge to rejuvenate the other impacted reefs during times
of disturbances.
Fish population was dominated mostly by herbivorous and algivorous fish composed
of very small sized individuals. High fish abundance was found in CCAs where the
commercial important sweetlips, parrotfish and wrasses were the dominant species.
Heavily fished reefs such as Mwazaro, Jiwe Jahazi and Mwarembo had lower fish
abundance. Groupers, snappers and emperors, which are the favourite and
commercially important target for fishers were either recorded in very low abundance
or absent altogether. This is a concern since these fish prey on other fish including
herbivorous fish (such as parrotfishes) that help in controlling the growth of
macroalgae that compete with corals for space, thus reducing coral cover. Further
low triggerfish (main sea urchin predators) populations observed are probably
responsible for increased populations of sea urchins. Apart from their removal of
coralline, calcareous and turf algae (though grazing activities on) that aid in the
settlement of coral recruits, the sea urchins, Echinometra mathaei, Diadema setosum
and Diadema savignyi are also major agents of biological erosion, eroding reef
substratum therefore further reducing coral cover and suitable substrate for coral
settlement. The high levels of urchin populations observed in the CCAs either
suggests slow recovery, early stages of the management intervention or illegal fishing
activities in these areas. Alternatively, these reefs are still at an early stage of the
recovery process.
Corallivorous fish such as butterflyfish are ecologically important. They feed on
corals but once the energetic value of their food source is depleted as a result of
disturbances brought about by anthropogenic disturbances, they move to other reef
areas. This could explain the low levels observed in most reefs in the Shimoni-Vanga
area (except Wasini CCA and Kiromo). This should be a concern to reef
conservationists and managers. Low coral cover and diversity at Mwazaro is largely
due exposure to sediment run off from River Ramisi. Sediment influx could be
playing a role in limiting coral cover and diversity by smothering coral and limiting
light for growth, in addition to aiding the recruitment of Crown of Thorn (COT)
starfish due increased nutrient influx associated with sedimentation and other
components river discharge.
During the February 2015 monitoring programme, plankton community structure and
abundance dwindle in comparison to the amelioration seen during the previous
monitoring campaigns hence need for intensified restoration activities to ensure a
sustainable plankton community assemblages.
31
2.5 Management recommendations and interventions
To address problems affecting reef habitat quality and marine resources in the south
coast (Funzi-Shimoni-Vanga) area, the following recommendations are made.
 Initiation of vigorous campaign programs to create awareness on the negative
impacts of overfishing and destructive fishing methods, degraded corals reefs
and the benefits accruing from sustainable exploitation, conserving and
management of coral reef areas.
 Introduction of coral reef restoration programs through coral transplantation to
accelerate the recovery of corals in degraded areas, especially within the
CCAs and use the programs as means to improve the skills, knowledge and
behavior of resource users/fishermen towards effective marine conservation
and management.
 Promotion of alternative livelihoods such as eco-tourism ventures/dive sites
around restored/transplanted areas, creation of mangrove nurseries,
introduction of mariculture/aquaculture activities in order to reduce
exploitative pressure on marine resources
 Involvement of a multi-sectorial management approach that includes all
stakeholders (fishing communities (BMUs), Department of Fisheries, Kenya
Wildlife Service, the tourism sector, agricultural and health sectors, and NGOs
for effective management of both the marine resources and the adjacent
terrestrial and catchment areas to reduce overexploitation as well as sediments
and nutrients influx into the marine areas
 Rotational closures, especially of open access reef areas needs to be
investigated. Rotational closure of some areas over 12 months should ensure
that areas of the reef are always closed to exploitation at any one point in time
to allow for the recovery of ecological and economically important reef
communities (e.g. herbivorous fish, sea urchin predators and the fishery
targeted carnivorous fish).
 Gear management policies should be considered, incorporated into the
existing management strategies and enforced so that destructive fishing
practices such as beach seine netting and spear gun fishing are controlled or
stopped completely.
 The capacity for local communities to manage their own marine areas needs to
be increased through appropriate training schemes and workshops.
 Existing coastal conservation strategies in the area such as the co-management
strategies underway in Wasini and Kibuyuni should be supported,
strengthened and expanded in order to improve the biodiversity and
productivity of coral reefs.
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2.6 References
Allen, G. R., 2005. Reef fishes of Northwestern Madagascar. In: McKenna S and
G.R. Allen (eds.) A Rapid Marine Biodiversity Assessment of the Coral reefs of
Northwest Madagascar. pp. 39-48.
McClanahan, T. R., Muthiga, N.A., Kamukuru, A.T., Machano, H., Kiambo, R.,
1999. The effects of marine parks and fishing on the coral reefs of northern
Tanzania. Biological Conservation 89: 161–182.
McClanahan, T. R., Shafir, S. H., 1990. Causes and consequences of sea urchin
abundance and diversity in Kenyan coral reef lagoons. Oecologia 83:362–370
Samoilys, M. A., Randriamanantsoa, B., 2011. Reef fishes of northeast Madagascar.
In Obura D., Di Carlo, G., Rabearisoa, A. and T. Oliver. (eds). A Rapid Marine
Biodiversity Assessment of the Coral Reefs of Northeast Madagascar. RAP
Bulletin of Biological Assessment 61. Conservation International. Arlington,
Virginia.
Sheppard, C. R. C., Obura, D. O., 2004. Corals and reefs of Cosmoledo and Aldabra
atolls: extent of damage, assemblage shifts and recovery following the severe
mortality of 1998. Journal Natural History 39 (2): 103–121.
Veron, J. E. N., 2000. Corals of the World. Australian Institute of Marine Science,
Townsville, Australia.
Wallace, C. C., 1999. Staghorn corals of the world: a revision of the genus Acropora.
Victoria: CSIRO Publishing
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