Benthic AssessmentsBenthic Assessments

One benthic ecologist’s concerns and One benthic ecologist’s concerns and suggestionssuggestions

Fred NicholsFred Nichols

USGS, retiredUSGS, retired

IntroductionIntroductionWhere I am coming fromWhere I am coming from

As a marine invertebrate ecologist, I want to As a marine invertebrate ecologist, I want to know why species live where they do. That is, know why species live where they do. That is, what determines their distribution and abundance what determines their distribution and abundance in space and time?in space and time?

With respect to evaluating human influences on With respect to evaluating human influences on invertebrates, it is important to first define natural invertebrates, it is important to first define natural variability, in both species and their environment.variability, in both species and their environment.

It is against the background of natural variability It is against the background of natural variability that the effects of human stressors should be that the effects of human stressors should be measured.measured.

Evolution of indices/assessmentsEvolution of indices/assessments(Nichols’ version)(Nichols’ version)

Long history of evaluating the relative abundance of Long history of evaluating the relative abundance of tolerant vs. sensitive species.tolerant vs. sensitive species.

The concept of trophic indices applied to continental The concept of trophic indices applied to continental shelves, e.g., organic enrichment off Los Angelesshelves, e.g., organic enrichment off Los Angeles

Index of Biological Integrity applied to freshwater systems, Index of Biological Integrity applied to freshwater systems, contrasting impacted with pristine streams or watersheds contrasting impacted with pristine streams or watersheds (James Karr)(James Karr)

EPA EMAP expanded a condition index concept to estuariesEPA EMAP expanded a condition index concept to estuaries

IntroductionIntroductionWhat we have learned about estuariesWhat we have learned about estuaries

Distribution and abundance are determined by many Distribution and abundance are determined by many factors such as dispersal of larvae, substrate type, factors such as dispersal of larvae, substrate type, food availability, predation, and physical stressors.food availability, predation, and physical stressors.

Abundances of individual species fluctuate widely Abundances of individual species fluctuate widely over time.over time.

Most species, particularly estuarine species, are Most species, particularly estuarine species, are durable – they tolerate a varying environment.durable – they tolerate a varying environment.

We continue to be surprised by the very large We continue to be surprised by the very large ecosystem changes that periodically occur (e.g., in ecosystem changes that periodically occur (e.g., in the benthos, plankton and fish communities).the benthos, plankton and fish communities).

Pectinaria californiensis

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Pectinaria californiensis

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IntroductionIntroductionWhat we have learned (2)What we have learned (2)

Most estuarine and coastal environments are Most estuarine and coastal environments are “somewhat” contaminated. “somewhat” contaminated.

At heavily contaminated sites, the effects are At heavily contaminated sites, the effects are usually obvious - few species survive. usually obvious - few species survive.

We are steadily making progress in understanding We are steadily making progress in understanding how individual species respond to contamination.how individual species respond to contamination.

Distinguishing clearly between the effects of Distinguishing clearly between the effects of natural factors and the effects of low to moderate natural factors and the effects of low to moderate contamination on community composition in contamination on community composition in estuaries has been exceedingly difficult, despite estuaries has been exceedingly difficult, despite decades of good effort. decades of good effort.

Role of Benthic AssessmentsRole of Benthic AssessmentsEMAP, IBI, etc.EMAP, IBI, etc.

It is indeed important to take geographically It is indeed important to take geographically comprehensive approaches in evaluating the comprehensive approaches in evaluating the condition of estuarine/coastal benthic habitats, condition of estuarine/coastal benthic habitats, e.g., the Triad approach:e.g., the Triad approach:

Define community compositionDefine community composition Assess contaminant distributions Assess contaminant distributions Carry out bioassaysCarry out bioassays

Such studies provide objective means of describing Such studies provide objective means of describing contaminant distributions and distinguishing those contaminant distributions and distinguishing those sites that seem to be most affected by sites that seem to be most affected by

contaminants.contaminants.

My Primary ConcernsMy Primary Concerns

A. Interpreting contaminant effects on communities A. Interpreting contaminant effects on communities from limited sampling in physically dynamic from limited sampling in physically dynamic environments.environments.

B. Tracking the status of environmental condition B. Tracking the status of environmental condition over time, i.e., trends.over time, i.e., trends.

A.A. Contaminant effects in dynamic Contaminant effects in dynamic environmentsenvironments

IInfluence of salinity (1)nfluence of salinity (1)

Benthic community structure in river-dominated Benthic community structure in river-dominated estuaries is in large part determined by physical estuaries is in large part determined by physical processes, of which salinity is a key indicator.processes, of which salinity is a key indicator.

Physically dynamic estuaries like San Francisco Bay Physically dynamic estuaries like San Francisco Bay exhibit large and often sudden changes in salinity. exhibit large and often sudden changes in salinity.

Species distributions and abundances can change Species distributions and abundances can change

dramatically in response to the changing conditions.dramatically in response to the changing conditions.

Contaminant effects in dynamic Contaminant effects in dynamic environmentsenvironments

Influence of salinity (2)Influence of salinity (2) EMAP-type studies, typically based infrequent sampling, EMAP-type studies, typically based infrequent sampling,

assume that the relationship between community composition assume that the relationship between community composition and salinity is defined at the time of sampling. and salinity is defined at the time of sampling.

Salinity measured at the time of sampling does not necessarily Salinity measured at the time of sampling does not necessarily define the conditions under which community composition was define the conditions under which community composition was established. established.

The benthic community in the upper reaches of the Bay can be The benthic community in the upper reaches of the Bay can be markedly influenced by water transport/salinity conditions markedly influenced by water transport/salinity conditions months before the time of sampling. months before the time of sampling.

The physical regime at the time of recruitment is probably a The physical regime at the time of recruitment is probably a much more meaningful influence on community structure than much more meaningful influence on community structure than physical conditions at the time that one collects adults.physical conditions at the time that one collects adults.

Contaminant effects in dynamic Contaminant effects in dynamic environmentsenvironments

Influence of salinity (3)Influence of salinity (3) Infrequent sampling means that important events Infrequent sampling means that important events

(storm, drought, flood, arrival of new predator, (storm, drought, flood, arrival of new predator, etc.) that determine species etc.) that determine species distributions/abundances are missed. distributions/abundances are missed.

One should have an understanding of antecedent One should have an understanding of antecedent physical conditions when interpreting community physical conditions when interpreting community composition at any moment in time. composition at any moment in time.

The combination of a fluctuating environment and The combination of a fluctuating environment and infrequent sampling makes the interpretation of infrequent sampling makes the interpretation of non-lethal human effects on community non-lethal human effects on community composition very challenging.composition very challenging.

B. Tracking environmental conditionB. Tracking environmental condition

Tracking environmental condition, including contaminant Tracking environmental condition, including contaminant effects, over time is critical to evaluating water quality effects, over time is critical to evaluating water quality management and policy decisions (adaptive management). management and policy decisions (adaptive management).

Geographically comprehensive but temporally limited Geographically comprehensive but temporally limited sampling, combined with natural variability and few sampling, combined with natural variability and few reference site options, can preclude meaningful biological reference site options, can preclude meaningful biological community trends analysis community trends analysis

The goal should be to develop strategies that provide The goal should be to develop strategies that provide resource managers and decision makers with defensible resource managers and decision makers with defensible “trends” information“trends” information

The challenge is to identify trends in human impacts (e.g., The challenge is to identify trends in human impacts (e.g., with the Triad approach) in shallow, physically dynamic with the Triad approach) in shallow, physically dynamic estuaries where the time scales of important natural change estuaries where the time scales of important natural change in the community are typically shorter or longer than most in the community are typically shorter or longer than most sampling frequencies.sampling frequencies.

Conclusions and Recommendations (1)Conclusions and Recommendations (1)

Distinguishing human-induced effects on estuarine Distinguishing human-induced effects on estuarine benthic community structure, other than at highly benthic community structure, other than at highly impacted sites, is a major and, I think, largely impacted sites, is a major and, I think, largely unmet challenge.unmet challenge.

To measure the effectiveness of actions taken to To measure the effectiveness of actions taken to improve conditions in estuarine systems, the next improve conditions in estuarine systems, the next generation of studies should focus on investigations generation of studies should focus on investigations designed specifically to evaluate trends, i.e., to designed specifically to evaluate trends, i.e., to measure both the short- and long-term patterns of measure both the short- and long-term patterns of variability and change in these systems. variability and change in these systems.

Such studies should incorporate measures of Such studies should incorporate measures of natural perturbations of the environment in the natural perturbations of the environment in the analysis of the effects of contaminants on analysis of the effects of contaminants on community structurecommunity structure

Conclusions and Recommendations (2)Conclusions and Recommendations (2)

Making substantial progress in evaluating the Making substantial progress in evaluating the effects of contaminants on the Bay’s ecosystem effects of contaminants on the Bay’s ecosystem will require will require deciding what tractable questions can be answered with deciding what tractable questions can be answered with

future assessment studies, andfuture assessment studies, and establishing permanent, frequently sampled sites in the establishing permanent, frequently sampled sites in the

areas of most concern.areas of most concern.

Because of the scope of the challenge, the Because of the scope of the challenge, the greatest focus should perhaps be on those areas greatest focus should perhaps be on those areas of San Francisco Bay that are known to be heavily of San Francisco Bay that are known to be heavily contaminated, with the goal of:contaminated, with the goal of: Distinguishing between natural and human induced Distinguishing between natural and human induced

impactsimpacts Tracking impacts over time to establish long-term Tracking impacts over time to establish long-term

trends.trends.

Conclusions and Recommendations (3)Conclusions and Recommendations (3)

We should urge more coordination among studies We should urge more coordination among studies of the benthos, plankton and fish communities of the benthos, plankton and fish communities because they are so closely interconnected in a because they are so closely interconnected in a single food web. Each of these communities is single food web. Each of these communities is critical to an understanding of overall conditions critical to an understanding of overall conditions and trends in the estuary.and trends in the estuary.

We need to pay attention to what the individual We need to pay attention to what the individual species themselves, by their distribution and species themselves, by their distribution and abundance patterns over time, are telling us about abundance patterns over time, are telling us about what is going on in the environment.what is going on in the environment.