Wave Exposure and its Effects on the Diversity of a Shoreline Anne Haley, Lauren Jonah, Riki Krentz,...

Wave Exposure and its Effects on the

Diversity of a Shoreline

Anne Haley, Lauren Jonah, Riki Krentz, Jessica Hingley & Caroline Méthé

Introduction - diversity

• Health and survival of ecosystem

• 2 variables: richness & evenness

• Two diversity indices: Shannon-Wiener and Simpson’s

• Physical & biological stressors affect diversity - eg. wave exposure

Wave Exposure

• Strong influence on diversity

• Contradictory past research in animal species

• More agreement in botanical species− Greater diversity in wave-exposed

Effects of wave exposure

• Research question: What is the optimal amount of wave exposure to yield the greatest diversity?

• Intermediate Disturbance Hypothesis

• Our hypothesis: greater diversity at moderate → high → low

• Three sites: low, moderate and high

Methods

• Indian Point, Greens Point and Bar road

• 10 quadrants of 1x1m

• 100m transect line

Methods

• Quadrant counts− Animal counts & estimates− % plant coverage

estimates

• Unknown species were taken back to the lab for further identification

Results

• No significant difference between sites− Data was not normalized

• Diversity indices− Moderate → Low → High

Results - Fauna

Results - Fauna

• Species diversity: moderate → low → high

• Moderate wave exposure = highest alpha

• Overall low beta (changeover in species)

Results - Flora

Results - Flora

• Species diversity: high → moderate → low

• High and low wave exposure = highest alpha

• Overall high beta (changeover in species)

Discussion

• Support for the intermediate disturbance hypothesis−Moderate wave exposure = greatest species

diversity

• High wave exposure sites did not have greater diversity than sites with low wave exposure

• These results were analyzed only on animal species, due to plant abundance was measured in percent coverage

Discussion

Crashing of waves on intertidal substrate (disturbance): independent variable

Habitat disturbances: −Renew limiting resources:

oxygen, nutrients−Prevent dominating species

Excessive amounts = unsuitable habitat

Discussion

High Wave Exposure

Greater number of plants• Plants are colonizers after disturbance due

to succession

No barnacles recorded • Desiccation, duration of emergence• Whiplash effect (Grant, 1997)

− Fronds physically remove barnacles with wave motion

• Interaction with whelks?

Discussion

Low Wave Exposure

Very few plants were found• Soft, muddy substrate which does not

provide a surface for fauna to grow

Areas for improvement• Samples collected from the immediate

surface• Some species gone unnoticed

• Brief sampling time (low tide)

• Estimations

• Varying counting methods

• Normalize data

• Inaccurate identification• Little differences in barnacle and periwinkle

species

Conclusions

• Species diversity was highest in areas with moderate wave intensity

• Proven by the intermediate disturbance hypothesis− Balance of disturbances yields the greatest

amount of species richness and evenness → diversity

Questions?