"We will study the feeding behavior of small coral reef blennies, fish that live in small holes on the surface of the coral reef and feed on zooplankton near the surface of the reef. "
Photos by Ray Clarke

Recent Projects

Civilian Research and Development Foundation: Evaluation of the Ecological Consequences of the human induced invasion of the ctenophore Mnemiopsis leidyi to the Caspian Sea

The Caspian Sea is a unique land-locked body of water with low salinity; it is considered the largest saline lake in the world. The surface of the Caspian Sea lies nearly 28m below sea level, and reaches a maximum depth of 980m. The natural resources of this unique environment are of world wide importance. The Caspian Sea produced 90% of the total sturgeon catch in the world. Sturgeons and black caviar are the best examples of the importance of Caspian Sea biodiversity for the Azerbaijanian economy.

Beginning in the 1980’s an exotic marine immigrant ctenophore Mnemiopsis leidyi was discovered for the first time in the Black Sea; 10 years later this species was found also in the Azov Sea. Finally, in 1999 this species was also present in the Caspian Sea (Zaitsev et al., 2001).

The prognosis for the effects of Mnemiopsis leidyi on the biological resources of the Caspian Sea is very pessimistic. It is predicted that in the next few years the pelagic food web of the South, Middle and part of the North Caspian Sea will be destroyed. There is a grave danger of loss of biodiversity of the unique ecosystem of the Caspian Sea and considerable economic loss of fisheries including all herring, gray mullet, sea sander, beluga and starred sturgeon fishes and the endangered Caspian seals.

The following research objectives were investigated:

Determine the distribution of Mnemiopsis leidyi in the Azerbaijanian area of the Caspian Sea (from Iranian to Russian borders) and its correlation with other groups of marine zooplankton. We will define the size structure and biomass of zooplankton to determine the potential food spectrum of Mnemiopsis leidyi, including both the juvenile (tentaculate) and adult (lobate) body forms. Special attention will be paid to the feeding of juvenile ctenophores on free living Protozoa (ciliates and testaceous amoebae) which constitue 43% of all planktonic fauna in the Caspian Sea.

All the proposed local research was done by Azerbaijanian scientists. During the first year Professor Edward J. Buskey (USA) visited Azerbaijan for joint discussions related to methods and approaches used in this study.

On the second year Dr. I. Alekperov visited the USA for joint experimental collaboration to plan and learn new methods of zooplankton investigations – to compare microscopic methods of enumerating Protozoa to semi- automated enumeration with an imaging flow-cytometer. This instrument counts the number of small plankton in live samples of sea water and takes a photograph of each one as they pass through.

Texas Higher Education Coordinating Board, Advanced Technology Program:  Application of cell recognition technology to environmental studies of harmful algal blooms

Harmful algal blooms such as the "red tide" caused by the dinoflagellate Gymnodinium breve cause major fish kills and economic loss along the coast of Texas.  The factors regulating these blooms are poorly understood, in part because of the difficult and tedious work associated with microscopic analysis of environmental water samples to examine for the presence of red tide cells when they are in low concentrations in nature (e.g. between blooms and during the early stages of bloom development).  This project would develop the use of existing technology (FlowCAM) to provide a system capable of automatic identification of red tide cells from seawater samples.  This system combines the cell discrimination capabilities of flow cytometry with automated image analysis.  Species of phytoplankton in the 10-1000 µm size range are characterized based on laser induced fluorescence and light scattering properties of individual cells in combination with digital imaging, storage and computerized analysis of images of each cell.  We would develop the species recognition parameters to adapt this system for identifying G. breve cells in Texas coastal waters.  This system would then be tested for use in monitoring of field samples and for use in laboratory/field studies of growth, grazing and toxic effects of red tide cells.  This system would reduce the workload for routine monitoring of coastal waters by government agencies, hatcheries and the mariculture industry and provide a powerful tool for environmental studies of harmful algal blooms.

NOAA Coastal Ocean Program: ECOHAB: The role of zooplankton grazing in harmful algal bloom (HAB) dynamics and trophic transfer of toxins

Project Summary: The objective of this research is to better understand the potential role of zooplankton grazers in the initiation and maintenance of harmful algal blooms, and to better define their role in the transfer of toxins through the food chain where they can potentially be ingested by humans or endangered wildlife species. This study is focused on the toxic dinoflagellate Karenia brevis (formerly Gymnodinium breve) which causes extensive fish kills, human health risk and economic loss along the Gulf of Mexico coast. Protozoan grazers have rapid growth rates and are the most likely grazers on harmful algal species to be capable of controlling blooms during their initial phase. Metazoan planktonic grazers such as copepods may also graze on harmful species, but their longer generation times make them poor candidates for controlling blooms. However, since some copepods tend to avoid consuming toxic phytoplankton species, they may switch to alternate prey, including protozoan grazers of harmful algal species, which may indirectly aid the formation or maintenance of blooms. A series of laboratory experiments is planned to measure the grazing and growth rate of zooplankton grazers on harmful algal blooms and the impact of metazoan planktonic grazers on the interaction between protozoa and harmful algae species, to determine the role of planktonic grazers in harmful algal bloom dynamics and as vectors to transfer toxins to higher trophic levels. Although several studies have shown that some species of harmful algae are not acutely toxic to zooplankton, there has been less study of sublethal effects of toxins on zooplankton. If these toxins, many of which act as neurotoxins, affect the behavior of zooplankton, this might make them more likely prey for visual predators. Changes in behavior could both make the zooplankton more conspicuous to their predators and might also reduce the efficacy of their escape behaviors. In this study we will use video computer motion analysis techniques to see if toxins produce abnormal swimming behavior in zooplankton that ingest them. We will also use high speed video to carefully examine the kinetics of copepod escape behaviors to see if zooplankton that ingest toxic algae have impaired escape responses, making them more likely prey and increasing the chances of biological magnification of toxins. If the opportunity presents itself, we will sample zooplankton during an outbreak of red tide along the Texas coast to examine feeding behavior of zooplankton under natural conditions and to test for copepod growth and toxin content within bloom areas.

Texas Sea Grant: Assessing the health of the planktonic food web in Texas coastal bays using RNA:DNA ratios

Zooplankton are an important link in the food web between phytoplankton and larval fish. It has long been known that adequate food supply is critical to successful recruitment of marine fish. While a number of studies have addressed the effects of natural and man-made disturbances on fish and shellfish populations, few studies have focused on lower trophic levels, which can provide important insights into recruitment processes. Marine copepods are normally the dominant zooplankton taxa, and their larvae (nauplii) are important food for larval fish. Assessing the vigor of copepod populations in nature can be attempted by measuring growth rates or egg production rates of females, but these methods involve tedious experiments with long incubation times. It would be a significant advance for routinely assessing the health of planktonic food chains if animals could be collected in the field from numerous locations and their condition reliably assessed based on a laboratory assay such as RNA:DNA ratio.

National Science Foundation: Sensory reception and predator evasion in crustacean zooplankton

This project will evaluate the roles of neuromotor processes in predator-evasion by calanoid copepods. Calanoids are one of the more important groups of animals on earth, outnumbering even insects, and dominating metazoan biomass. Despite their importance to oceanic ecosystems, critical information is missing on their behavioral strategies for survival, the morphological specializations of the sensory and motor systems that underlie this success, and the physiology of these systems. We propose to develop a broad-based view of copepod predator evasion behavior and ecology through a focus on sensory triggering of their escape behavior. Our working hypothesis is that like other aspects of predator evasion, escape behavior exhibits distinctive variations among species, reflecting differences in strategy for animals inhabiting different pelagic environments. Physiological, morphological and behavioral approaches will be used in parallel to study the escape behavior quantitatively. In the previous project period, we measured reaction times and force production during escape triggered by hydrodynamic disturbances. We discovered that calanoid copepods are about the fastest-reacting metazoans known. Some species are capable of reacting within 2 ms. Part of the explanation was found in an electron microscopic study: the particularly fast copepods, unlike their slower cousins, possess myelin, a multi-layered cellular wrapping of nerve axons that greatly speeds the conduction of nerve impulses. We find too that calanoid copepod muscle physiology is remarkable. Energy output per gram equals or exceeds any yet measured in other animals. In adaptations ranging from sensory to motor, copepods seem to break many of the "rules" established in larger animals. The work proposed will examine the differences in physiological and behavioral characteristics of hydrodynamically triggered evasion behavior and correlate them with morphological adaptations of the nervous system, especially myelination. Threshold sensitivities, reaction times, escape kinematics, force and energy production, response durations, swimming speeds and distanced jumped will be studied in different groups and related to phyletic and ecological standing. The role of photoreception in escape behavior will be explored both by itself and in combination with mechanoreception. Quantitative data on sensitivity to increases and decreases in light intensity at different background levels, and altered mechanoreceptive and photoreceptive responsiveness in the presence of stimulation from the other modality will be compared among taxa and ecologies. The properties of habituation, recovery from habituation, and dishabituation will be compared among species. The project will provide quantitative information on the unusual sensory and physiological adaptations of the neuromotor systems that contribute significantly to survival strategies in an animal group of central importance to the oceanic food web.

NSF Grant OCE-9711233 "Aggregative behavior of zooplankton: In situ and laboratory studies of copepod swarms and mysid schools"

Zooplankton aggregations such as swarms and schools occur on scales ranging from centimeters to meters (and greater) and have important implications for trophic dynamics in the sea. The formation and maintenance of these aggregations has a strong behavioral component, although hydrodynamics also play an important role in the location and nature of these aggregations. In mangrove prop root habitats there are two excellent examples of aggregative behavior in zooplankton: the swarming behavior of the copepod Dioithona oculata and the schooling behavior of the mysid Mysidium columbiae. Previous studies have examined the swarming behavior of D. oculata in situ, studied the role of photoreception in swarm formation and maintenance and examined the metabolic costs of swarming behavior. This study will focus on several unanswered questions regarding copepod swarms and begin studies of schooling behavior of mysids.

The swarming behavior of D. oculata has a strong diel component; swarms form at dawn and disperse at dusk. During the night, currents disperse the copepods into adjacent channels and bays, up to tens of meters from the mangroves. One objective of this study is to determine the sensory information used by D. oculata to find its way back to the mangrove habitat at dawn. It is hypothesized that the copepods (whose ares are not capable of image formation) use the angular distribution of light underwater to locate the horizon, and orient their swimming toward it. Another objective is to carefully investigate the value of swarming behavior as an anti-predation adaptation; this will be done for both visual predators (planktivorous fish) and non-visual predators (cubozoan medusae). D. oculata swarms are also found near coral reefs, where environmental and optical conditions are quite different from mangrove habitats. Swarms near coral reefs will be studied in situ, and the factors affecting swarm formation and maintenance in these environments will be quantified. It is thought that light reflected off the bottom is used as a swarm marker for copepods on coral reefs, but that hydrodynamics also plays an important role in swarm location, since swarms often form in the lee of coral heads.

Mysidium columbiae is a holoplanktonic mysid that schools in shaded areas near mangroves. It's well developed compound eyes are thought to have limited visual acuity but highly developed movement perception; visual cues are thought to play an important role in schooling behavior. The role of vision in the schooling behavior of this species will be investigated by determining the visual threshold and visual acuity of this mysid. The adaptive value of schooling as an anti-predation device and metabolic costs of schooling behavior will also be investigated.

Zooplankton aggregations such as copepod swarms and mysid schools represent one end of a continuum of plankton patchiness from those controlled mainly by the behavior of the organisms to those controlled mainly by physical concentrating mechanisms. By achieving a better understanding of the factors influencing behaviorally controlled zooplankton aggregations, the range of potential contributions of behavior to other forms of patchiness will become clearer. By understanding the adaptive value of swarming and schooling behavior in zooplankton, the potential effects of patchiness on plankton trophic dynamics will be revealed.

NSF Grant OCE-9529750 "Why has the Texas brown tide persisted for over 5 years?"

The Texas brown tide has persisted in the Laguna Madre for 5 years. This bloom has disrupted the basic food web in the Laguna Madre by reducing seagrass biomass and altering the composition and diversity of benthic and planktonic grazer communities. The factors that lead to the initiation of the bloom are well documented, but the most important question remains: why has the bloom persisted for so long? We propose to address this question in a systematic way starting with two basic hypotheses. The first is that the persistence of the brown tide is the result of this algal species out-competing other species for essential resources. The brown tide could do this by being better adapted to the wide range of temperature and salinity conditions found in the Laguna Madre, by making more efficient use of existing nutrient conditions, or by interfering with the growth of other species through allelopathic agents. Laboratory studies indicate that the brown tide alga can not use nitrate as a nitrogen source. We will perform field mesocosm experiments to investigate the effects of nutrient additions on brown tide growth and phytoplankton species composition and perform laboratory studies of algal growth rates to explore light, temperature, salinity and allelopathic effects. Our second major hypothesis is that the persistence of the brown tide results from the breakdown of grazing controls. To address this hypothesis, we will carry out field studies in the transition zones between areas where the brown tide dominates and where the brown tide is not present, and examine the changes in the balance between growth and grazing processes in these transition waters. We will also study the toxic and/or inhibitory effects of the brown tide on the feeding and growth of microzooplankton grazers to investigate if there is a threshold concentration of brown tide below which these effects are not seen. We will also investigate the possibility that the inability of protozoan grazers to control the brown tide may be due at least in part to a rearrangement of the food web in the Laguna Madre, where microzooplankton grazers are no longer food limited but are now predator limited by copepods and other mesozooplankters with no alternative food sources. We plan to test this hypothesis using mesocosm studies in which copepods will be added or excluded, and we will follow changes in the planktonic community.

NSF Grant OCE-9521375 "Sensory reception in crustacean zooplankton"

This project will evaluate roles of mechanoreception in predator detection in calanoid copepods. Neurophysiological, morphological and behavioral approaches will be used in parallel to generate a broad -based integrated view of copepod predator-evasion behavior and ecology through a focus on their mechanosensory systems. In the first year, behavioral and physiological experiments using similar stimulation protocols will be used to establish how well physiologically recorded activity correlates with behavioral responses. The hypothesis to be tested is that escape behavior is being triggered by mechanical stimulation of two specific neurons (GAMs) in each antenna. A second focus for the first year will be a comparison of conditions eliciting bioluminescent discharge in mesopelagic copepods with those leading to the stereotyped rapid escape "jumps", both in relation to the discharge of sensory neurons. In the second and third years, work in these areas will be carried further, examining the differences in evasion behavior in several species from different ecological situations. The physiological basis of habituation and altered responsiveness to repeated attack stimuli will be investigated. The results will be interpreted in relation to the role individual species play in the oceanic food web.