Download The Affect of Substrate on Intertidal Macrofauna Species Distribution

The Effect of Substrate on Intertidal
Macrofauna Species Distribution in
Southern New Brunswick
Melyssa Baker, Sarah DeBay, Chelsea Dickie, Brie Nelson, & Rachael Coon
Dr. Aiken
BIOL 3361
Objective:
To assess the ecological importance of intertidal
substrate on habitat preference of the
Southern New Brunswick intertidal fauna in
order to gain a better understanding of the
factors affecting habitat preference.
Substrate and its importance in habitat
selection:
STRESS
• Solid bedrock is a stable, reliable substrate
type under stress because of its immobility.
Substrate and its importance in habitat
selection:
ENVIRONMENTAL HETEROGENEITY
• Environmental heterogeneity, including
variation in substrate, in combination with
interspecific niche differentiation, positively
correlates with species richness.
Substrate and its importance in habitat
selection:
INTERMEDIATE DISTURBANCE HYPOTHESIS
• Species richness was highest in the
“intermediate substrate”.
Sand = Unstable environment.
Bedrock = Increased risk of predation.
Substrate and its importance in habitat
selection:
MICROHABITATS
• Another reason that the site with
intermediate substrate may have the highest
species richness is that the intermediate
substrate offers more potential microhabitats.
Hypotheses:
1. Nature of substrate will influence species
richness and diversity of macrofauna.
2. Hard substrate will be preferable to soft
substrates for a larger number of intertidal
species.
Study Sites
Mace’s Bay
Indian Point
Bar Road
Materials and Methods
• Three locations
• 100 m line transect
• Quadrat (1m2) placed at
10 meter intervals
Within each quadrat
- substrate type and % area estimated
- counted resident organisms
- identified resident organisms
Substrate and Fauna
Species Richness Between Sites
Mace’s Bay
Species Richness
16
Indian Point
18
Bar Road
11
Figure 1- Species Richness between the three areas of study.
Species Richness At Each Site
Species Richness
Bedrock
Bedrock/Loose
Substrate
11
Sand/Mud
Mace’s Bay
7
6
Indian Point
15
12
10
Bar Road
N/A
N/A
11
Figure 2- Species Richness within a site comparing the three different substrates; bedrock, intermediate,
and sand or mud.
Species Count
Species count
Mace's Bay
100
90
80
70
60
50
40
30
20
10
0
Bed rock
Covered bedrock
Mud/sand
Figure 3- Depiction of the species observed at Mace’s Bay and the prevalent habitat on which they were
found. Species average was calculated from the amount of species observed on the various substrates.
Species Count
Indian Point
100
Species count
80
60
40
20
Bed rock
Covered bed rock
Sand/mud
0
Figure 4- Species average was taken for the amount of species found on the three various substrates to
calculate average prevalence. Many different species were present but in low quantities, most habitats
were dominated by the same prevalent species.
Species Count
Species count
Bar Road
100
90
80
70
60
50
40
30
20
10
0
sand/mud
Figure 5- Depiction of the prevalence on species found in/on the sand and mud at bar road. Averages were
taken from each quadrant for each individual species.
Five Dominant Species
100
80
spcies count
60
Bedrock
40
Intermediate
Sand/Mud
20
0
balanoides
littorea
obtusata
testudinalis
edulis
-20
Figure 6- Demonstration of the five most prominent species found at the study sites. The prevalence of each
species on the three various substrates are shown. An average of the number of species found on each substrate
was taken from the three study sites.
Indian Point Observations
• At Indian Point several species were found
under large yet movable rocks that were not
observed anywhere else in the sampled
quadrates.
– Asteria vulgaris the purple starfish
– Asterias forbesil another type of starfish
– Carcinus maenas the green crab
– Cancer borealis the Jonah crab
– Strongylocentrotus droenbachiensis the sea urchin
Microhabitat
• Pressures facing species that inhabit the intertidal
zones often force species to select microhabitats such
as crevices or vertical surfaces to avoid potentially
deadly conditions (Branch 1988).
• This pattern of distribution can be explained as the
area under the rocks/cobble provide a unique
microhabitat that meets the needs of these species by
giving them protection from the harsh physical
properties of the intertidal such as wave action and
desiccation as well as an escape from predators.
Examples of Microhabitats
• Sea urchin juveniles
– shelter beneath cobbles as a refuge from
predators such as rock crabs, lobsters, and fish
• Crabs
– seek out refuge under rocks as a means of
predator avoidance and to deal with the varying
water levels
5 Major Species:
1. Semibalanus balanoides
(Acorn Barnacle)
2. Littorina littorea
(Common Periwinkle)
3. Littorina obtusata
(Flat Periwinkle)
4. Acmaea testudinalis
(Tortoiseshell Limpet)
5. Mytilus edulis (Blue Mussel)
Mytilus Edulis
• Found on all substrate types
• Role on Hard Substrate:
• Interstitial Spaces
• Role on Soft Substrate:
• Interstitial Spaces and hard attachment site
Semibalanus balanoides
• Found across all sites
• S. balanoides and M. edulis in competition
• Lower limit likely caused by M. edulis
competition, upper limit determined by abiotic
factors.
• Clustered distribution due to larval preferences
Acmaea testudinalis
• No clear preference for substrate type, found
on all
• Prefers vertical surfaces during the day,
horizontal at night
• Largest amount found at Indian Point living on
bedrock
Littorina obtusata
• Prefers hard substrate (bedrock and
intermediate substrate) for a strong hold
• Most were found at Indian Point
• Most commonly found on intermediate
substrate – interstitial spaces offer protection
Littorina littorea
• Most found at Mace’s Bay and Indian Point
• Preferred hard, intermediate substrate
• Migrates towards water in winter – less
exposure time
Mace’s Bay:
-Greatest species evenness
-High Richness
-Mace’s Bay likely displays the
substrate preferred most by intertidal
fauna
(Bedrock with intermediate overlay)
Indian Point:
-Not Evenness, but Dominance
of 4 focus species
-Highest Richness
-But mainly in areas with
conditions that mirror
Mace’s Bay
Bar Road:
-No Solid substrate (VERY unlike the other two sites). Just intermediate stones
sitting atop the mud.
-Least species richness, diversity, and evenness.
-We do see very clear dominance of M. edulis, and somewhat of S. balanoides
-Reasonable to say that our hypothesis is supported by our results.
-Most organisms prefer the bedrock substrate with some intermediate overlay.
-Mace’s Bay showed all 3 substrates, but preference for the bedrock areas was the most
common.
-Further supported by Indian Point, a site which was predominantly bedrock and
intermediate, which showed:
-Species Richness
-Dominance of 4 Focus Species
-All 4 species were found settled on bedrock areas, rather than sand patches.
100
Five Dominant Species
spcies count
80
Figure 6
shows a defined
60
preference
for bedrock.
40
Bedrock
Intermediate
Sand/Mud
20
0
balanoides
-20
littorea
obtusata
testudinalis
edulis
-While M. edulis flourished in the muddy conditions, the other 3 out
of the 5 key species have next to no desire for sand/mud as a
substrate.
-The organisms that were tabulated in sand and mud, were
found suckered onto intermediate stones (hard substrates)
that were found within/around the mud.
100
Sand/Mud
80
Specues Count
60
40
20
0
balanoides
-20
littorea
obtusata
testudinalis
edulis
-Hard substrate provides stability , holdfast attachment,
protection, and in some ways shelter.
-4 of the 5 Focus species were seen thriving and
competing on the bedrock areas of Indian Point,
and Mace’s Bay.
-Whereas sand/mud is not very useful, providing neither
protection nor stability, and prone to frequent
disturbance.
-Less species richness and diversity seen in mud.
-M. edulis is well suited for the mud environment
-Didn’t have much competition amongst the few
species that were found within Bar Road.
This supports our hypothesis:
The nature of the substrate will influence the richness and
diversity of its fauna.
-Bedrock and mud obviously differ in the genre of species
they attract, and the number/richness of such species.
The harder substrates are more attractive places to settle for
most intertidal macrofauna, because of their stability.
-More species richness seen at Maces Bay and Indian Point
-4 out of the 5 Focus species thrive on Bedrock,
-1 out of the 5 thrives in Mud
Sources of Error:
-Organisms possibly miscounted/misidentified.
-Large margins were observed in results
-Water submergence
G. duebeni
Water Fleas
100
-Distance from water’s edge
Sand/Mud
Specues Count
80
60
40
-S. balanoides quadrat within Bar Road 20
-More balanoides found in 1 Quadrat at 0
Bar Road than all of Indian Point or
Mace’s Bay’s total count.
balanoides
-20
littorea
obtusata testudinalis
edulis
Conclusions
• The nature of the substrate does influence the
species richness and diversity of the fauna.
• Hard substrates are preferred by more species.
• Soft substrate have limited species richness.
• Heterogenous substrate supports greater
species richness.
• Life history strategies of intertidal fauna tend to
be specific to a substrate -> habitat preference
Questions?