NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 1
Questions from reading and discussion section (10 points each)
Reading - Hughes 1994
According to Hughes, what is the effect (direct or indirect) of heavy fishing in the Caribbean on the
abundance of:
1) Diadema- 3
2) Algae- 3
3) Corals- 3
Fishing- direct reduction of fishes
Fish eat algae (1), indirect positive (1) effect on algae (1pt)
Algae compete with corals (1pt), indirect negative effects (1) on corals (1)
Fish eat/compete with diadema (1), indirect positive effect (1) on urchins (1)
What are two other factors (besides fishing) which may have affected the abundance of (any of) these
populations?
1pts
Eutrophication (.5)
Disease (.5)
Reading – Doherty 1983
Doherty manipulated the presence of the damselfish, P. wardi, on patch reefs and compared
recruitment (density of recruits) of larval P. wardi to patch reefs with and without residents. What was
the result of these manipulations? What did he conclude and what are the broader implications of these
results in terms of what limits the size of reef fish populations?
Manipulation 1: w/out residents, mostly replenished by larval recruitment P. wardi (2), no difference in
recruitment, no difference in post-settlement mortality
Manipulation 2: w/ residents, no difference in recruitment, no difference in post-settlement mortality
For both manipulations (2) no difference in recruitment, (2) no difference in post-settlement mortality
(2) Concluded that recruitment of P. wardi do not affect recruitment or moratlity of larval mortality
Implication:
(2) Recruitment limitation determine population size of coral reef fish
Extra credit: (1) size of larval recruits was influenced by P.wardi
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 2
Reading- Ebert and Russell 1988
Ebert and Russell looked at the relationship between the size frequency distribution of purple sea urchin populations
and the location of these populations along the coast. What was the pattern that they found and what was their
explanation for this pattern?
Pattern: 4PTS
Higher proportion of small urchin (1) above headlands (1),
Even size freq below headlands, and uneven size freq (1). above headlands (1)
Explanation 6pts
Advection  of larvae (1) from areas above headlands (1), leads to episodic and lower recruitment (1)
Eddies and retention of larvae (1) from area below headlands (1), have higher and consistent
recruitment (1)
Compare and Contrast (6 points each) - (should be able to define each term (can be graphical), give
example of each and show how each member of the pair differs.
1) Replication vs. psuedoreplication
2) Proportional vs. switching vs. keystone predation
3) Species diversity vs. species richness
4) Closed vs. open populations
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 3
5) Settlement vs. recruitment
3pts a) settlement - the permanent transition from the pelagic environment to the benthic environment
i.e. from the planktonic dispersive stage to the sessile/sedentary benthic stage
3 pts b) recruitment - broadly, the addition of individuals to a population
Short Answer Questions (10 points each)
1. In theory, what is the relationship between diversity and disturbance? Describe the basis for the
relationship. Give an example that supports the theory.
2 ways to answer this question IDH and the other is
compensatory mortality
IDH: intensity, frequency or time sense that
relationship (6)
Graph
Example (4)
OR
compensatory mortality: description (6)
mortality is disproportionately greater in competive
dominat, simply because more abundant
-frequency dependent
-sources of mortality include predation and disturbance
Example (4)
2. What is the logic of experimental controls? You may use examples to support your answer.
4pts Experimental control is a group of experimental subjects that is not exposed (2pts) to a treatment
being investigated so that it can be compared (2pts) with experimental groups that are exposed to the
treatment
Experimental controls are used in scientific experiments to prevent factors other than those being studied
from affecting the outcome.
2pts: example
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 4
3. Define stability in terms of resistance, resilience, elasticity and amplitude.
3pts resistance, community/population persist, unaltered when exposed to a source of
perturbation
3pts resilience, community returns to equilibrium following perturbation
2pts elasticity, how fast a community returns to equilibrium
2pts amplitude, magnitude of perturbation that a community can return from
4. Describe the hypothetical general relationship between settlement and subsequent adult density.
Indicate on your graph the regions that are dominated by density-dependent and density-independent
processes.
Graph (6pts)
Description (4pts):
1. That # of adults is in large part determined by larval supply
and the # of settlers(
2. If instead adult density is unrelated to larval supply/
settlement; then the most influential processes occur POSTsettlement, therefore  decoupling local reproduction and
subsequent local settlement is unimportant to regulate and
stabilize (
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 5
Question 4 Con’t
(d-i) settlement is important and limiting but
only to a certain point, where (d-d) postsettlement processes
eventually overwhelm variability in
settlement (i.e. increasing
settlers has no affect on population size)
5. List one physical and one biological process that is important in the following life-history
phases of marine organisms: Reproduction, transport, delivery, settlement, recruitment.
1pt for each example
physical
Reproduction
Transport
Delivery
Settlement
recruitment
Temporal/seasonal
Large scale
current
Advection: CA
current, EL
Nino, La Nina
Turbulence,
current speed,
Space
availability
Larval behavior
Biogenic
habitat
Timing
location
Internal waves
Current speed
biological
Sexual maturation
Open vs closed
Density dependent
Larval size
fecundity
Larval duration
Windward,
Leeward
Internal waves
Vertical
distributionontpgeny,
Ecological
filters
Stratified in
water
Competition
Predation
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 6
Essay Questions (20 points each)
1) Menge and Sutherland have proposed a set of rules for the importance of various factors in
determining the structure of intertidal communities along a gradient of environmental harshness. These
rules can be represented graphically. In the figure below: (1) label the x and y axes (2pts) and indicate
direction of scale(2pts) (e.g. does the scale of the x axis increase as you move from left to right), (2)
label (2pts) each of the three lines. Describe (14pts) (i.e. write) the basis of these rules in the space
below the figure.
label the x and y axes (4pts)
indicate direction of scale(1pts)
label (3pts) each of the three lines
Describe (12pts)
3pts A) In habitats with relatively benign physical environments (1) – predation (2) structures
communities
3pts B) With increasing environmental harshness - predation efficiency is decreased and
competition becomes a major process structuring (3)
3pts C) With even greater environmental harshness - importance of competition decreases and
physical processes become more important (3)
3pts D) Local escapes from predation (in benign environments) or physical stress (in harsh
environments) cause patchiness in the community (3)
From the Experiment
Different processes are important at exposed and protected sites:
a) at exposed sites, predation/grazing unimportant - competition is the primary
organizing force in the system.
1) Predators are generally uncommon
2) Mussels are competitively dominant (over algae and barnacles)
b) at protected sites, predation important
1) with predation barnacles dominate if Fucus is removed
2) without predation mussels out-compete barnacles and algae
3) predation keeps competition from occurring with mussels (mussel abundance is kept
low). What about competition between barnacles and Fucus?
c) Importance of predation varies with exposure; at exposed sites predators are
uncommon, their feeding ability is reduced because they have to spend more time
hanging on and not feeding (is this because they are snail predators and grazers?)
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 7
Essay Questions (20 points each)
2) For each of the following four hypotheses generated to explain the maintenance of species diversity (i.e., coexistence of
competitors), (1) explain the hypothesis, (2) describe its assumptions, and (3) describe its predictions.
Niche Diversification (5pts) 1 pt for description, 2 pt assumptions, 2 pts predictions
- Disturbance interrupts successional sequence by creating patches of different ages � different states of
succession. In absence of disturbance, succession leads to climax community characterized by
monospecific stand of competitive dominant (or a few) / low diversity. But, at extremely high levels of
disturbance, nothing or only a few species of rapid colonizers (or disturbance tolerant species) would
persist ,low diversity. Recall that competitively superior species typically have poor colonizing
capabilities.
Assumptions:
a) competition based (assumes resources are limiting)
b) resource partitioning (each species is a superior competitor for particular resources or within particular
niche)
c) for test, assume perturbation does not alter resource availability, only diminishes species abundances
Predictions:
a) total number of individuals and total number of species limited by resources, ⇒ assemblage-wide
carrying capacity (K)
b) relative abundance of spp. determined by relative niche availability ⇒ specific carrying capacity for
each species
c) predictable composition and relative abundance
Lottery Hypothesis (5pts) 1 pt for description, 2 pt assumptions, 2 pts predictions
Space on the reef is limiting, until it open unpredictably. Where upon larvae from an abundant, diverse
larval pool would settle in the open patch strictly by chance.
Assumptions:
• competition based (resource limitation)
• larval pool saturates resource (space)
• no resource partitioning (all species equal competitors)
• likelihood of creating and acquiring resource (space) due to
random chance (deaths and larval settlement unpredictable)
• equal likelihood of settlement from larval pool
Predictions:
• unpredictable as to what species will recruit to any location or at any time
• maximum total abundance across species (K)
• relative abundance of species fluctuates unpredictably
• including after perturbation
Storage Effect (5pts) 1 pt for description, 2 pt assumptions, 2 pts predictions
attempts to explain that the temporal recruitment fluctuations among species can lead to stable
coexistence of competitors. Coexistence will occur when there are constant or varying environments.
Three essential conditions that would permit patterns of stable coexistence in systems where recruitment
was space limited: (1) early vital rates and larval supply among species is variable across years; (2) adults
survive over long periods of poor recruitments; and (3) episodic recruitments (high rates of settlement)
are matched by generation time.
NAME:____________________________________________
2009 Exam - Marine Ecology 108; page 8
Assumptions:
• competition based (resource limitation)
• same assumptions as lottery hypothesis, but
• relative recruitment success of species changes through
time (akin to “gradual change” hypothesis)
• variable success due to variation in larval production,
planktonic conditions, settlement conditions
• species persist through bad recruitment periods and “store” recruitment events in extended lifetime (age
classes) of adults
Predictions: same as Lottery Hypothesis but different mechanism
Recruitment Limitation (5pts) 1 pt for description, 2 pt assumptions, 2 pts predictions
Larval supply limits recruitment below that which is required to saturate resources
Assumptions:
• Assumes high mortality of pelagic larvae limits number of recruits to benthic populations
• Larval supply limits recruitment below that which is required to saturate resources
• No competition so mortality is density-independent
Predictions:
• total numbers and relative abundance fluctuates with variable larval supply