Jeroen Gerritsen

• PhD
• Principal Investigator at Tetra Tech

Heavy precipitation events and subsequent high flows are occurring with greater frequency and intensity, which could have substantial implications for biomonitoring programs that typically evaluate changes in biological condition due to stressors at local and watershed scales. In this study we evaluated response and recovery of macroinvertebrate co...

The Biological Condition Gradient (BCG) is a conceptual model that describes changes in aquatic communities with increasing levels of anthropogenic stress. The gradient represented by the BCG has been divided into 6 levels of condition that biologists consider readily discernible in most areas of North America. We developed quantitative BCG models...

The Wyoming Department of Environmental Quality (WYDEQ) initiated development of regionally-calibrated biological criteria for assessing the ecological condition of streams across the state. They intend to use the biological criteria to evaluate the overall ecological condition of their streams and watersheds, and to justify listing and delisting s...

Human activities such as mining, logging, agriculture, and residential development have degraded biological conditions in many West Virginia (USA) streams. Using benthic macroinvertebrates as biological indicators of stream condition, the West Virginia Department of Environmental Protection (WVDEP) identified streams across the State that do not me...

The eastern panhandle region of West Virginia is entirely within the Appalachian Ridge and Valley ecoregion. It is underlain by limestone in the eastern part and by shale and sandstone in the western part. Agricultural and urban development has affected the condition of the streams of this region. We examined samples from 165 stations in the Ridge...

The Clean Water Act of the USA as a Basis for BioassessmentConsistency in Sampling Methodology in Diverse RegionsSampling Designs for BioassessmentReference Condition is Central to BioassessmentsVariability of Biological DataThe Future of Bioassessment in the USAReferences

The relationships among nutrients, benthic algal community, and aquatic plant biomass were examined in 21 different streams in Montana's Hi-line region, in the Northwestern Glaciated Plains ecoregion. We examined habitat, physical and chemical characteristics, aquatic macrophytes, and benthic algae in the stream segments. Based on multiple lines of...

Human activities such as mining, logging, agriculture and residential development have caused biological degradation to streams of West Virginia. Total Maximum Daily Loads (TMDLs) are being developed for all biologically-impaired streams within the state, and require causes of impairment to be identified so that pollutants can be controlled. Using...

There are two objectives of this project: 1) developing biological indicators that characterize urban stressors, and 2) establishing reference conditions for urban systems. Our dataset was assembled from multiple, routine biological monitoring programs in Baltimore, MD/Washington, DC, Cleveland, OH, and San Jose, CA, representing data from approxim...

Human activities such as mining, logging, agriculture and residential development have caused significant biological degradation to many streams of West Virginia, USA. Employing benthic macroinvertebrates as biological indicators of stream health, the West Virginia Department of Environmental Protection (WVDEP) has identified streams across the sta...

The new European assessment system for freshwater ecosystems is based on reference conditions. As the ecological status of rivers must be determined with respect to the near-natural reference conditions focus is given to establish a typological framework. A basic part of this typology is the ecoregion approach. Multivariate analysis of the benthic...

We investigated four stream types in four different bioregions, classified by catchment area and altitude, and stressed by different degrees of organic pollution and habitat alteration. We examined a macro-invertebrate based multimetric approach for Austrian rivers as a potential assessment method within the European Water Framework Directive. Bent...

It can be difficult to unambiguously establish the influences of a particular stressor or group of stressors in a complex ecosystem, except, perhaps, when the effects are extreme (Luoma and Carter, 1991). Yet this is a critical problem we face when attempting to understand the influences of human activities on ecosystems. Single experiments or stud...

Here we ask what types of field studies can best detect interactions among stressors and allow us to separate and rank the relative importance of individual stressors in systems receiving multiple disturbances (natural and/or anthropogenic). If multiple stressor responses are common in nature, then single variable tests, such as analysis of a bioma...

In this chapter, we discuss how environmental variability affects the exposure of organisms and ecological systems to stressors, and give guidance on how to understand influences of stressors. We consider the characteristics of environmental variability and issues relating to the measurement of environmental variation. We discuss how to select the...

All article in German

Planning and implementation of wetland sample surveys requires consideration of several statistical design issues. Issues regarding the planning of a survey include the specification of what questions are to be addressed, the population of interest, and reporting units. To obtain a representative sample and unbiased estimates of environmental param...

Classification of waterbodies is a necessary step for aquatic biological assessment. Geographic classes, such as physiographic provinces, marine biogeographic provinces, and ecoregions are frequently used as a classification framework for conducting bioassessments. An alternative to such a priori classification of waterbodies is to let the biologic...

This paper summarizes and synthesizes the collective results that emerged from the series of papers published in this issue of J-NABS, and places these results in the context of previously published literature describing variation in aquatic biota at landscape spatial scales. Classifications based on landscape spatial scales are used or are being e...

A collaborative study among 6 states along the mid-Atlantic seaboard of the USA developed a consistent approach for collecting and interpreting macroinvertebrate data for low-gradient streams of the coastal plain. The study had 3 objectives: 1) to evaluate the validity of aggregating reference site data into a single bioregion, 2) to select biologi...

This paper presents the approach used in the technical development of assemblage-level biological indicators in two widely disjunct areas of the United States (the ecoregions of Wyoming, and the Chattooga River Watershed in Georgia), and how they have been, or will be, used. The State of Wyoming has been sampling benthic macroinvertebrate, physical...

Our study developed an approach to biological assessment that would document effects of pollution on benthic macroinvertebrate assemblages in Florida streams. The primary objectives were: (1) to classify streams for assessment of benthic assemblages and (2) to develop biological metrics and aggregated indices for biocriteria and assessment. Referen...

Episodic acidification is common in poorly buffered streams of the coastal plain in the Chesapeake Bay watershed, and may harm sensitive life stages of migratory fish that spawn in small streams of the region. We developed a model to predict the risk of episodic acidification in these streams that is likely to be harmful to juvenile fish. Risk pred...

The goal of this document is to help states develop and use biocriteria for streams and small rivers. The document includes a general strategy for biocriteria development, identifies steps in the process, and provides technical guidance on how to complete each step, using the experience and knowledge of existing state, regional, and national surfac...

A probabilistic mathematical model of bivalve suspension-feeding in estuaries is based on bivalve abundance, filtering capacities, and water mixing parameters. We applied the model to five regions of the upper Chesapeake Bay, ranging from shallow tidal fresh habitats to deep mesohaline habitats, for the years 1985 to 1987. Model results indicated t...

Maryland's Department of Natural Resources has ongoing commitments to investigate the chemical and biological effects of acidic deposition in Maryland. An important step in this process is understanding and developing management strategies to assess the problems associated with acidic precipitation. The project involved conducitng a literature revi...

A large proportion of streams in western Maryland are subject to acidification and subsequent loss of biological resources. A decision support approach was applied to aid in selecting streams as candidates for liming to mitigate effects of acidification. The objective of mitigation is restoration and protection of balanced populations of indigenous...

The study forms part of an ongoing process to develop understanding of the effects of acidic deposition in Maryland and to develop tools for managing its consequences on natural resources. Episodic acidification is common in poorly buffered streams of the Coastal Plain of Maryland and may harm sensitive life stages of migratory fish that spawn in s...

The Environmental Monitoring and Assessment Program (EMAP) is a comprehensive, multiagency program designed to assess the condition of the nation's ecological resources at national, regional, and subregional scales. Data and information collected by EMAP will be integrated with data from other monitoring programs and environmental information of ot...

The document contains the appendices A-J for the 3 volume series. Volume 2 covers: Nitroarenes; Food chain module; Plant and animal bioconcentration factors and pollutant loss rates for terrestrial food chain model; Review and comparison of currently recommended methods for computing dry deposition velocity; Carcinogenic synergy; Inhalation risk co...

A comprehensive, multipathway health-based risk assessment study was performed for routine air emissions from three combustion sources collocated at a rural site. The sources included a proposed 2250 ton/day municipal waste resource recovery facility, an existing 558 MW coal-fired power plant, and a proposed 750 MW oil/gas-fired combustion turbine...

The biological consequences of instituting a summer minimum flow from the Conowingo Hydroelectric Dam were investigated by comparing invertebrate abundance in the Susquehanna River during 1980, when flow shutdowns were frequent, to that in 1982, when the minimum flow (142 m3 s−1) was maintained. The minimum flow was only maintained from April 15 to...

Episodic acidification from acidic precipitation in Coastal Plain streams of the Chesapeake Bay watershed is a potential threat to spawning and survival of anadromous fish species. The study is part of a process of selection of streams for mitigation of acidic episodes to increase the spawning success of anadromous fish stocks. It describes the dev...

Long-term monitoring of macrobenthic resources was carried out for the Maryland portion of Chesapeake Bay and its major tributaries. Sampling covered 70 stations, some with a data record going back to 1971. Macrobenthic animals fill several trophic and functional roles in the Bay ecosystem, including suspension feeding, surface deposit feeding, sub...

The document contains the appendices K-N for the 3 volume series. Volume 3 covers: Toxicological profiles; Detailed results of exposure assessment and risk characterization; Systems Applications, Inc. (SAI) discussion on wet deposition; and Reviewers' comments and responses.

Overview of 3-volume report. The report presents an overview of a comprehensive, multipathway health-based risk assessment study performed for routine air emissions from three combustion sources collocated at a rural site. The sources included a proposed 2,250 ton/day municipal waste resource recovery facility, an existing 558-MW coal fired power p...

Seedling germination from the seed banks of two marshes in the Okenfenokee Swamp, a deep macrophyte marsh and a shallow sedge marsh, was examined in the greenhouse under three hydrologic regimes and four nutrient conditions. Experimental hydrologic conditions of 3-mo duration, were constant exposure (no standing water), 1-mo exposure followed by re...

Fluorescent dyes and particles, epifluorescent microscopic video image analyses and high-speed microcinematography were used to determine fluid flow and particle capture by Daphnia magna and D. pulex. These fluorescent techniques detected processes that could not be seen or differentiated by direct observation with light microscopy due to their hig...

Electrophoretic mobility (EM) was measured on natural particles from 11 southeastern U.S. lakes and streams. The mobility decrcascd with increased conductivity, increased with dissolved organic carbon (DOC), and increased with pH. EM was further measured in each water sample with pH adjusted over the pH range 3-10. In general, mobility increased wi...

Following a severe drought, changes in macrophyte species composition and biomass dynamics were monitored in four marsh plant communities within the Okefenokee Swamp, located in southeastern Georgia and northeastern Florida, U.S.A. Marshes with three distinct patterns of water-level fluctuation were examined from April 1982 to January 1985. Two con...

Feeding of protozoan and crustacean zooplankton was analyzed by flow cytometry (FCM), resulting in direct counts of particles ingested by each individual. Ciliates ( Cyclidium sp.) were allowed to feed on Microcystis aeruginosa and analyzed directly on a flow cytometer for cyanobacterial autofluorescence coincident with each ciliate. Numbers of Mic...

We develop an energy-balance foraging model for swimming animals with the following components: power input, power spent foraging, and metabolic rate. The model can be expressed in terms of animal length, animal swimming speed, and food (prey) density; it is then applied to low, medium, and high Reynolds number swimming of protozoa, zooplankton, an...

Ecological disturbance is defined in context of a dictionary definition and state-space system theory. Disturbance can be partitioned into cause and effect. The cause is the exogenous disturbance, and its effect is unusual behavior of system state or output, referenced to nominal behavior. A disturbance can act on input, state, or the coupling para...

The model illustrates the transition from cruising to ambush predation as prey swimming speed increases. The transition is abrupt for protozoa swimming at low Reynolds number, but it is more gradual for fish swimming at high Reynolds number. Consideration of fluid mechanics leads to the conclusion that filter feeding with reciprocating appendages i...

The functional response of an organism is often assumed to maximize its fitness. We examined the relationship between functional response and body growth, survivorship, and reproduction in Daphnia magna under controlled and comparable conditions. In a previous study we determined that D. magna exhibits a Holling Type II functional response with an...

Cyclomorphosis of Bosmina (Eubosmina) tubicen , expressed as allometric growth of antennules and mucrones, was followed in five populations in the Okefenokee Swamp. Allometry of antennules was strongly cyclical, being positive in fall, winter and spring, but negative in early summer. Antennule allometry and other morphological variables (egg size,...

Abstruct Swimming patterns, fecging behaviors, and ingestion, filtering, assimilation, and respiration rates were measured for Daphnia mugnu in food concentrations from 0 to 10" Chlamydomonas reinhnrdi cells * cm-", equivalent to O-20 mg C* liter-'. A Helling type 2 functional response curve or an Ivlev model without a threshold appear to be biolog...

Surface chemistry of both particles and animals is important in filter feeding at low Reynolds number. Daphnia magna, fed mixtures of three sizes of polystyrene particles, retained particles that were smaller than the mesh size of the animals (1.0 micrometer) at greater efficiencies than predicted by a sieving model. Retention efficiency of the sma...

Daphnia magna, Daphnia pulex, Daphnia paruula, and Daphnia Eaevis respond to small temperature changes by changing the duration and frequency of upward swimming, in pro- portion to the rate of change of temperature. When temperature rises, animals swim up more frequently in direct proportion to the rate of change of temperature. In falling temperat...

We delimit a cylindrical attack field for a Chaoborus larva feeding on zooplankton, and propose a mathematical model to predict encounter rates with prey for this ambush predator. The model is based on the encounter process between a stationary cylinder and spheres moving at constant velocity in random directions. The predictions of the model are c...

A model is developed to predict the minimum population density required (critical density) for successful sexual reproduction in animals. The model predicts that: (1) Hermaphroditic reproduction requires only half the critical density of bisexual reproduction; (2) a linear increase in mortality results in an exponential increase in critical density...

A model of random encounters among zooplankton shows that encounter probability depends on the encounter radius, density of prey, and swimming speeds of both predator and prey. The model predicts two optimal tactics for efficient predators: ambush and cruising. Swimming direction influences encounter probability; cruising predators can maximize the...

Predator–prey interactions between swimming animals of the zooplankton are studied in a mathematical model. The assumptions are: 1) the animals are points in a 1-m3 homogeneous space, 2) the animals move at random and are randomly distributed, and 3) the predator animal has an encounter radius given by its sensory system. The mathematics of encount...