The effects of substrate types on species diversity

Michelle Johnson, Amanda Jeanson, Marshall Elsemore, & Aneri Garg

Outline ● Background● Hypothesis● Methods● Results● Discussion● Conclusion

Study Site

Physical and Biological Stress

● Wave exposure

● * Tidal height *

● Competition

● Predation

Substrate Cover

Substrate Type Proportion on large islands and mainland of Quoddy Region (%)

Bedrock 35.2

Coarse Sediment 55.1

Mud 9.2

Salt Marsh 0.5

Substrate Impact - Sand

● Sand/Mud: o Heavily modified by tides, wind, storm surges

o Less vegetation

o Low-medium diversity

o Burrowing organisms

Substrate Impact - Cobbles

● Cobbles:o Colliding rock and debris from wave action

o Diversity dependent on local features & positioning

o Low species diversity

Substrate Impact - Rock

● Bedrock: o Development of tide pools and crevices

o Promote high diversity

o Mediate thermal stress

Hypothesis

● Difference in diversity between all 3 substrate types

● Highest diversity on rocky substrate

H0 :There is no difference in diversity between all 3 substrate types

Materials

• 100m measuring tape• 1m square quadrat• Ziploc bags for species collection• Camera

Methods• 2 transects were set up at separate locations based on differences in:

• Vegetation cover• Wave action• Substrate size

• Ten quadrats were placed along each transect.

Methods Cont’d

• Each organism found was collected, while

taking note if the specimen found was

present on the surface of the substrate or

underneath the flora cover.

• G. oceanicus and B. balanus were

unable to be collected due to difficulties

in handling their large numbers.

Different Substrate Types

● Large Rocks ● Cobbles ● Sand

Analysis● Species richness● Species diversity

o Shannon-Wiener Indexo Simpson`s Index

● Cochran`s Q Testo Nominal data

*Scuds and barnacles removed from the analysis

Results

Continued Results

Table 1: Species diversity for different substrate

Boulders Cobbles Sand

Species Richness 8 2 1

Shannon-Weiner Index 0.657 0.276 0

Simpson`s Index 3.5 1.8 1

Statistics

● Cochran`s Q Testo X2 = 0.503

o X2crit(.05, 8) = 14.067, and p < .05

o Reject the null hypothesis

A difference in diversity between substrate

Accepting our Hypotheses

Results supported our hypotheses:• Diversity on the three substrates differed and that with

the highest species diversity was indeed found on the

large rock substrate (aka boulders)

Implications with past Literature

High Diversity within Large Rocks

Bertness (2006)• Muscle bed protection from physical factors

• Diversity: crabs, limpets

Seed (1996)• Species evenness allows few abundant species• Leads to increased diversity

Peterson (1991)• Availability of rock space controls diversity levels and not prey availability

• Our experiment suggests:• Prey availability competition leads to lower levels of diversity than competition for

space

Implications with past Literature

Low Diversity within Sand/Rock

Donovan and Tyrell (2005)• Ease in modification of this substrate from high winds, waves and storms lower diversity in this

substrate• Species that live in this substrate tend to be burrowing species.

• Burrow for protection

Limitations

• One sampling site: Physical factors skew data

• Equipment: Inability to count all species in Quadrats

• Tide Movement: Inconsistent tide levels in the two sampling sites.

Conclusion• This experiment looked to:

• show a difference in diversity based on the type of substrate sampled.• Our results showed:

• A difference in diversity between the three substrates investigated in this experiment.

• Increased diversity on large rock substrates (boulders). • **The results supported work found in past literature and supported

diversity theories mentioned. • This Experiment Demonstrated:

• Substrate type seems to have an effect on species diversity (although many other factors also play a role).