Laboratory Aquaria Research Articles

Identifying Environmental Conditions to Promote Species Coexistence: An Example with the Native Barrens Topminnow and Invasive Western Mosquitofish

Coexistence of a native and invasive species may be possible at certain conditions along an environmental gradient where the individual responses of each species are maximally apart. Water temperature may differentially affect the growth of a native cool-water species like the Barrens topminnow, Fundulus julisia, and an originally warm-water adapted western mosquitofish, Gambusia affinis, who is a recent invader in Barrens Plateau region of middle Tennessee. We measured the specific growth rate (SGR) of the two species separately in laboratory aquaria at 10, 15, 20 and 25 °C, representing a range of temperatures that occur in topminnow habitats throughout the year. Both species grew faster with increasing temperature and SGRs were highest at 25 °C. The interspecific difference in SGR was maximized at 15 °C. At this temperature, mean growth rate of topminnows was 0.78% per day, more than twice that of mosquitofish (0.38% per day). These results suggest that cool springhead habitats with a near-constant thermal environment of 15 °C throughout the year may provide a growth advantage to the Barrens topminnow over the mosquitofish. Other environmental, density-dependent, or behavioral factors not examined here may act along with temperature to mediate the coexistence of the topminnow and mosquitofish.

Eutrophication-induced changes in benthic algae affect the behaviour and fitness of the marine amphipod Gammarus locusta

This study, conducted in mesocosms, natural field sites, and in laboratory aquaria, showed that eutrophication altered the nutrient status and dominance patterns among marine macroalgae, which in turn, stimulated gammaridean density. Gammaridean abundance correlated positively with both nutrient addition and the amount of green algae (also stimulated by nutrient enrichment). Path analysis indicated that the direct effect of nutrients on gammaridean density was of less importance than the indirect effect through increased production of green algae. In cage colonisation experiments, either in the field or in a control mesocosm kept under ambient nutrient conditions, more gammarids colonised nutrient enriched algae (E-algae) than algae with ambient nutrient levels (A-algae). Gammarus locusta generally grew faster on nutrient enriched algal specimens and when reared on green rather than on brown algae (fucoids). The nutrient status of periphytic algae did not affect gammaridean growth significantly, but the number of egg-carrying females (and thus egg production) was significantly higher among gammarids reared on E-periphyton. The gammaridean habitat preference order (red > green > brown > periphyton) was almost the reverse of their growth rate in feeding assays (periphyton > green > brown). This implies that macroalgae may be more important as a habitat than as a food source for these animals, which then have to become mobile in search of optimal food items. In this process, algal nutrient content was important as the gammarids in our study actively chose high quality nutrient-rich food, which, in addition, increased their fitness. Stimulated growth rates and egg production may ultimately lead to population increase, which, combined with the preference for high nutrient food items may dampen the initial effect of nutrient enrichment (i.e. blooms of green macroalgae) in shallow coastal waters.

Burrow structure, burrowing and feeding behaviour of Corallianassa longiventris and Pestarella tyrrhena (Crustacea, Thalassinidea, Callianassidae)

The behaviour of the Caribbean Corallianassa longiventris and the Mediterranean Pestarella tyrrhena, two burrowing thalassinideans, was studied in situ and in laboratory aquaria. Burrows of C. longiventris were closed most of the time; they consist of a deep U (down to 1.5 m) with upper and deeper chambers, some of them filled with macrophyte debris. The burrows of P. tyrrhena reached down to a maximum depth of 54 cm and consisted of a shallow U with a mound and a funnel, and a spiral shaft from which several, often debris-filled chambers branched off. The appearance of C. longiventris at the sediment surface to collect debris is strongly triggered by wave swell or odours from plant and animal juices; its burrows are opened within 10 min. The surface activity of P. tyrrhena was relatively less frequent and less predictable. Inside the burrows, both species exhibited different patterns of time allocated to 25 defined behavioural states. After being offered seagrass debris, P. tyrrhena spent relatively less time manipulating this debris, but it handled sediment more often than C. longiventris. During frequent mining events, both species showed sediment-sorting behaviour, which brought a parcel of sediment in close contact with the mouthparts; some of this sediment may be ingested because the fecal rods produced by both shrimps contain very fine sediment particles. Seagrass debris is irregularly tended by P. tyrrhena after its introduction into the chambers. Such material ultimately becomes buried. Corallianassa longiventris frequently returns to its debris chambers to pick up pieces of seagrass, which are subsequently cut with the chelae or ripped with the third maxilliped and then transported to another empty chamber nearby. Pieces become smaller with time and show curved cutting edges and bite marks. After 100 to 140 days, 2 to 6 g(dw) seagrass debris are consumed in this manner by individuals of this species. The debris-related behaviour of P. tyrrhena probably enriches the sediment around the burrow for stochastic encounters during later mining events. Such an indirect benefit may also be effective on a population level because other individuals may also encounter this buried nutrient source.

Impacts of mosquitofish, Gambusia affinis, on black mudfish, Neochanna diversus

The potential for western mosquitofish, Gambusia affinis, to negatively affect populations of black mudfish in New Zealand wetlands was investigated with annual fishing surveys of the Whangamarino wetland and by laboratory experiments evaluating competition and predation of mosquitofish on mudfish adults and larvae. Abundance of mudfish juveniles was reduced in the presence of mosquitofish at marginal wetland sites close to permanent water, but mosquitofish were not found at ephemeral adult mudfish habitats. In constructed wetland microcosms, mosquitofish reduced both growth and condition of post‐larval mudfish but did not attack or kill mudfish. In laboratory aquaria, mosquitofish rapidly consumed mudfish fry but survival time of the latter was significantly extended by an increase in density of submerged structures and by the presence of an alternative food source for mosquitofish. Because mosquitofish cannot survive in ephemeral wetlands that dry over summer, the impacts of mosquitofish on mudfish are likely to be minimal except in habitats where mosquitofish can survive year‐round owing to the presence of permanent standing water.

Chronic biotoxin-associated illness: Multiple-system symptoms, a vision deficit, and effective treatment

Blooms of toxigenic organisms have increased in spatial and temporal extent due to human activities and natural forces that alter ecologic habitats and pollute the environment. In aquatic environments, harmful algal blooms pose a risk for human health, the viability of organisms, and the sustainability of ecosystems. The estuarine dinoflagellate, Pfiesteria piscicida, was discovered in the late 1980s at North Carolina State University as a contaminant in fish cultures. P. piscicida was associated with fish death in laboratory aquaria, and illness among laboratory workers who inhaled the mist above aquaria. Both the fish and humans exhibited signs of toxicity. During the 1990s, large-scale mortality among fish and other aquatic organisms was associated with high concentrations of Pfiesteria sp. in estuaries on the eastern seaboard of North America from New York to Texas. Illness among humans was associated with direct exposure to estuaries and exposures to estuarine aerosols around the time of Pfiesteria-related fish kills. This review of the scientific literature on associations between Pfiesteria and human illness identified some of the possible mechanisms of action by which putative Pfiesteria toxins may have caused morbidity. Particular attention was given to the Pfiesteria-associated, human-illness syndrome known as Possible Estuary Associated Syndrome (PEAS). PEAS was characterized by multiple-system symptoms, deficits in neuropsychological tests of cognitive function, and rapid and severe decrements in visual contrast sensitivity (VCS), an indicator of neurologic function in the visual system. PEAS was diagnosed in acute and chronic illness cases, and was reacquired during re-exposure. Rapid normalization of PEAS signs and symptoms was achieved through the use of cholestyramine therapy. Cholestyramine, a non-absorbable polymer, has been used by humans to lower cholesterol levels since it was approved for that use by the U.S. Food and Drug Administration in 1958. When dissolved in water or juice and taken orally, cholestyramine binds with cholesterol, bile acids, and salts in the intestines, causing them to be eliminated rather than reabsorbed with bile during enterohepatic recirculation. Cholestyramine also has been reported to bind and eliminate a variety of toxic substances. The efficacy of cholestyramine therapy in treatment of PEAS supported the hypothesis that PEAS is a biotoxin-associated illness.

Antipredator responses to skin extract of redbelly dace, Phoxinus eos, by free-ranging populations of redbelly dace and fathead minnows,Pimephales promelas

Fishes in the superorder Ostariophysi possess specialized epidermal cells that contain a chemical alarm cue. The alarm cue is released when the skin is damaged during a predatory attack. Therefore, the cue serves as a reliable indicator of predation risk to nearby conspecifics and ecologically similar heterospecifics with which it shares predators. Antipredator behavior in response to these alarm cues has been demonstrated in numerous studies in confined spaces (laboratory aquaria, field traps, fluvarium). When tested on a natural field population however, behavioral response has been inconsistent. Here, we expose free-ranging redbelly dace and fathead minnows to skin extract of redbelly dace and record their behavioral response with an underwater video camera. We observed avoidance of areas in which skin extract was introduced, but no avoidance of areas in which water (control) was introduced. These data confirm the ecological function of skin extract in mediating predator–prey interactions in aquatic habitats, and argue against the hypothesis that alarm reactions are an artifact of confined spaces.

Spawning of Hexaplex (Trunculariopsis) trunculus (Gastropoda: Muricidae) in the laboratory: description of spawning behaviour, egg masses, embryonic development, hatchling and juvenile growth rates

Summary Some authors have studied and described different aspects of the reproductive cycle of Hexaplex (Trunculariopsis) trunculus, but most data are quite ancient and fragmented, lacking information in important respects on the reproductive cycle of this species. Based on several individual and collective spawns deposited in laboratory aquaria, this study provides additional and more detailed information on the spawning behaviour and egg-laying pattern, description of the general morphology and dimensions of the spawns, egg capsules, eggs, embryos and early post-metamorphic juveniles, as well as the first data available on the growth rate of T. trunculus hatchlings and juveniles (until 4 months old). Females deposited an average of 118 ± 89 tongue-shaped egg capsules per individual spawn, measuring on average 5.5 mm length x 4.7 mm width x 2.6 mm thickness. These egg capsules contained 723 ± 66 eggs with an average diameter of 240 ± 8 μm. T. trunculus is a direct developer species (metamorphosed hatchlings) with an incubation period of approximately 1 month. At hatching, individuals measured 1.64 ± 0.22 mm shell length and presented a growth rate of 2.5 mm/month at the end of 4 months. The breeding habits, embryonic development, hatchling and juvenile growth rates are discussed in terms of their implications for the management of the artisanal fishery for T. trunculus in the Ria Formosa lagoon and the assessment of the potential of this muricid species for molluscan aquaculture.

Vitellogenin in rare minnow ( Gobiocypris rarus): identification and induction by waterborne diethylstilbestrol

Rare minnow ( Gobiocypris rarus) is a tiny Chinese carp that has a short life cycle and is easily cultured in the laboratory. In this study, juvenile rare minnows were exposed to waterborne diethylstilbestrol (DES) at 0.05, 0.5 and 5 μg/l in laboratory aquaria. After exposure for 4, 8, 13 and 21 days, juvenile fish were collected and vitellogenin (Vtg) was measured in whole body homogenates. Native and SDS electrophoresis followed by Western blotting were performed for Vtg identification, and a non-competitive ELISA was developed. In the DES exposure groups (0.5 and 5 μg/l DES), Vtg appeared after 4 days, increased significantly after 8 days and reached a maximum on day 13. Further, a significant increase in the hepatosomatic index (HSI) was found in the 5 μg/l DES exposure group after 21 days. These results indicate that rare minnow provides a good model for assessing endocrine disruption by environmental estrogens.

The continuity and intensity of ultraviolet irradiation affect the kinetics of biosynthesis, accumulation, and conversion of mycosporine‐like amino acids (MAAs) in the coral Stylophora pistillata

Colonies of Stylophora pistillata unexposed to ultraviolet radiation (UVR) in laboratory aquaria contained minimal amounts of mycosporine‐like amino acids (MAAs). The concentration of MAAs increased rapidly during exposure to broadband UVR, then stabilized between 14 and 28 d of exposure. The four MAAs known to be produced by diverse zooxanthellae (Symbiodinium spp.) in culture were the first to increase in coral colonies, followed by six additional MAAs. Decreases in these four primary MAAs between days 14 and 28 were balanced by stoichiometric increases in the six secondary MAAs, suggesting a precursor‐product relationship. Discontinuing UV exposure caused rapid declines in the concentrations of primary MAAs, while secondary MAAs continued to increase, likely a manifestation of different rates of turnover of the putative enzymes involved in the de novo biosynthesis of primary MAAs and their conversion to secondary MAAs. The continued production of certain MAAs after UV exposure ceased indicates that UV is not required catalytically but is a signal that induces the enzymes of the biosynthetic pathway. Biochemically inhibiting the biosynthesis of primary MAAs after a pool of these MAAs had accumulated did not affect their conversion to secondary MAAs. Doubling the UV irradiance increased the rate of accumulation, first, of primary MAAs and, later, of secondary MAAs. Under normal UV irradiance, the eventual decline in the accumulation rate of primary MAAs was quantitatively explained by their conversion to secondary MAAs. Under doubled UV irradiance, where MAA concentrations were higher, the deceleration of accumulation of primary MAAs was twice as great as the acceleration in secondary MAAs, suggesting a regulation of the de novo biosynthesis of MAAs, perhaps by their own progressive, concentration‐dependent attenuation of UVR.

GETTING BIGGER FASTER: MEDIATION OF SIZE-SPECIFIC MORTALITY VIA FUSION IN JUVENILE CORAL TRANSPLANTS

Size-specific mortality can determine whether coral transplants become successfully established in a reef rehabilitation effort. Presented here are results of a study of size-specific mortality in laboratory-cultured transplants, and the mediating effect of fusion on their survival and growth. Culturing seeded colonies for transplantation minimizes impacts to source reefs. This strategy provides an opportunity to enhance survival of a transplanted population by incorporating selected aspects of colonial modular biology, such as fusion, into the culture phase. Despite efforts to develop a completely field-based method, settlement and early survival of juveniles of the scleractinian Pocillopora damicornis were much higher in laboratory aquaria than among those settled on reef substrate, highlighting the difficulty of direct seeding and justifying the higher effort involved in laboratory rearing. Juvenile colonies from four size cohorts (≤3 mm, 3.1–6 mm, 6.1–10 mm, and 10.1–29 mm), outplanted to a reef in August 1997, showed one-year survival of 0%, 2.5%, 16.3%, and 47.5%, respectively, illustrating significant size-specific mortality. Colony fusion resulted in lower 6-mo mortality (unfused colonies: 34.5% ± 0.4%, fused pairs: 14.0% ± 2.5%, fused groups: 8.3% ± 4.8%; means ± 1 se), and chimeras of >2 fused colonies produced polyps faster. Tissue necrosis along fusing colony borders was observed between 8-mo-old colonies. This suggested a rejection response, though colonies fusing prior to this age remained stable for up to one year. A transition matrix revealed that fused colonies showed greater probability of growth to the next size class, while unfused colonies showed higher mortality and stasis. Growth trajectories based on transition probabilities suggested that fused colonies would reach reproductive size much earlier than unfused colonies. To test the hypothesis that larvae aggregatively settle to increase their chances of fusing, settlement patterns were determined in larvae of same- vs. mixed-parent groups. Settled larvae were aggregatively distributed, with no difference in aggregation strength in larvae of same- vs. mixed-parent groups. Results suggest a benefit of fusion to survival and growth within the first eight months in juvenile coral colonies. Fusion could be used as a strategy to obtain larger colonies faster, provided they remain stable over time. Laboratory seeding and rearing of juveniles to 10 mm provides a workable alternative to fragment transplantation in brooding coral species, and similar strategies may also be developed for spawning species.

Is there a fish alarm cue? Affirming evidence from a wild study

Chemical alarm cues released from injured tissue are not released under any other context and therefore reliably inform nearby prey of the presence of a predator. Laboratory and field studies have demonstrated that most aquatic taxa show antipredator responses to chemical alarm cues. Ostariophysan fish (e.g. minnows) possess specialized skin cells that contain an alarm chemical. Magurran et al. (1996, Proceedings of the Royal Society of London, Series B, 263, 1551–1556) were the first to use underwater video to carefully document the behavioural response of free-ranging wild populations of minnows to minnow alarm cues. They found no evidence of an antipredator response, and challenged the assumption that the contents of these cells indicate risk in the field. They proposed that alarm responses are context dependent in that they are an artefact of enclosed environments such as laboratory aquaria and field traps. Here, we repeat their experiment on free-swimming field populations of littoral fish and report a significant decrease in the number of fish in areas where chemical alarm cues of blacknose shiners, Notropis heterolepis (Ostariophysi: Cyprinidae) were released. The effect of these chemical cues was equal in magnitude to the effect of the presentation of a model predator. The response to the approach of a model predator (visual cue) was intensified by pre-exposure to chemical alarm cues. We corroborated this interaction between chemical and visual indicators of predation risk in a laboratory study using glowlight tetras, Hemigrammus erythrozonus (Ostariophysi: Characidae). Response to the visual stimulus of a predator was significantly intensified by previous exposure to conspecific chemical alarm cues. We conclude that ostariophysan skin indeed contains an alarm cue that (1) informs nearby prey of imminent predation risk, (2) induces some form of antipredator behaviour in most contexts, and (3) affects subsequent behavioural responses to stimuli in other sensory modalities.

Effects of light intensity and spectrum on fish behaviour in laboratory aquaria

Teleost fish are commonly used as model species in laboratory studies of behaviour and ecology. In comparison to other groups of vertebrates used routinely in such studies, however, relatively little attention has been paid to their environmental requirements from a welfare perspective. Fish naturally inhabit a wide variety of aquatic habitats that differ enormously in the range of light environments they provide, and light regime has enormous potential to affect behaviour. Yet the level and quality of illumination (in terms of intensity and wavelength spectrum) provided in experimental studies of fish behaviour is generally designed to maximize ease of recording by the observer. In addition, display or home aquaria provide illumination that maximizes the ‘viewing pleasure’ of the observer, and specialist lighting tubes are available to stimulate rapid plant growth and to ‘show off’ the colours of fish, rather than to provide ‘natural’ light environments. Here we present the results of three studies designed to examine the effects of light intensity, wavelength spectrum and their interactions on the behaviour of a model species commonly used in behavioural studies, the three‐spined stickleback Gasterosteus aculeatus. Our aims are to determine whether unnatural light environments, generated by manipulating light intensity and wavelength spectrum, affect behaviour in ways that may lead to concern for the welfare of fish as research animals or pets.

Adaptations of subtropical Venus clams to predation and desiccation: endurance of Gafrarium tumidum and avoidance of Ruditapes variegatus

Intertidal endobenthic bivalves are often dislodged from sediments by hydrodynamic forces. As a result, they encounter the dangers of predation and desiccation, which are generally harsh near the sediment surface. To cope with such dangers, the bivalves possibly possess: (1) a strong body to endure predation and desiccation stress, (2) quick mobility to avoid the stresses, or (3) a high growth rate for attaining a size refuge. The present study examined which of these modes are adopted by the subtropical cobbled-shore Venus clams Gafrarium tumidum (Roding, 1798) and Ruditapes variegatus (Sowerby, 1852), revealing the following interspecific differences. (1) G. tumidum survived better than R. variegatus did in harsh experimental conditions, namely: the experimental cages exposed to predation and desiccation on a cobbled shore; a laboratory aquarium with a predatory crab Scylla serrata; and ovens with high temperatures (27°C and 34°C). (2) R. variegatus was more mobile than G. tumidum was, digging into the sediment on a cobbled shore more rapidly at both high and low tides. (3) The two species with shell lengths 20–30 mm showed similar growth rates (median: −0.2 to 44.5 μm day−1) in seasonal mark–recapture surveys over 2 years. Overall, to cope with the dangers of predation and desiccation G. tumidum appears to have a strong body, while R. variegatus displays rapid mobility, and neither species seems to attain a size refuge through rapid growth. Such species-specific modes are discussed in relation to the interspecific differences found in shell morphology.

Aspects of the biology of the burrowing shrimpAlpheus glaber(Olivi) (decapoda: caridea: alpheidae) from the Central Adriatic

Abstract The burrowing behaviour and burrows of the snapping shrimp Alpheus glaber are described from laboratory observations of animals collected by trawl at 72 m depth off Ancona, Central Adriatic. Resin casts of burrows were taken in laboratory aquaria. At depths of 35–78 m off Ancona, burrows consistent with those seen in aquaria were observed using underwater television. A single specimen of A. glaber was seen retreating into a burrow. A morphometric analysis demonstrated differences in relative growth between the sexes that may be related to reproductive biology of A. glaber. Analysis of stomach contents of several demersal fish and large decapod Crustacea provided evidence of the role of A. glaber in the food-web of the muddy trawling grounds exploited by the local fishing fleet.

The influence of social rank in the angelfish, Pterophyllum scalare, on locomotor and feeding activities in a novel environment.

To investigate differences in behaviour associated with social rank and environmental conditions, a comparison was made between swimming and feeding activities of dominant and subordinate angelfish, housed in groups of six, with those of angelfish housed singly in identical laboratory aquaria. Subordinate individuals were less active, less ready to feed and consumed less food items than dominants, but their feeding and activity levels were still greater than those displayed by isolated fish used as controls. When fish from each of the above categories were transferred to a novel, identical tank to be tested individually for a 6-day period, little change was observed in previously isolated fish. In contrast, the previous social experience had a marked influence on the behaviour of the other individuals, the effects being related to the social status. The strongest initial response to the new environment was shown by subordinate individuals, with a significant increase in swimming and a significant decrease in feeding compared to the group situation. Subordinates were significantly more active than dominants, who in turn moved more than previously isolated fish. Dominants and subordinates were now similarly reluctant to feed, and their food consumption was less than that of previously isolated fish. With time in the novel environment a significant reduction of swimming activity and a recovery of feeding measures were detected, but levels were still depressed in relation to the group condition, and lower in subordinates than in dominants, indicating the long-lasting effects of the previous social interactions. The results have clear implications for laboratory studies using groups of fish in which social hierarchies may be established prior to individuals being tested singly in a novel environment.

Copepodid Stages of Critomolgus Anthopleurus (Copepoda, Poecilostomatoida, Rhynchomolgidae)

Five juvenile copepodids of Critomolgus anthopleurusKim, 1996, were obtained by rearing the copepod and its actiniarian host for 10 days within a laboratory aquarium. Copepodid I of C. anthopleurus shows significant morphological differences from previous records. At this stage of C. anthopleurus, the antennule is 4-segmented, with 3 setae on the first segment; the antenna has a rudimentary exopod; the mandible has 2 armature elements in addition to distal lash; and the maxilliped is 4-segmented, with an armature formula 1, 2, 1, and 3. Sexual dimorphism first occurs at copepodid V of the maxilliped, which differs between sexes. A comparison of the maxillipeds of copepodid I between C. anthopleurus and other lichomolgoid copepods resulted in a conclusion that the maxillipedal endopod of the lichomolgoid copepodid I is fundamentally 2-segmented, with 1 seta on the first segment, and 3 setae and a setiform process on the second segment.

Aqueous-phase disappearance of atrazine, metolachlor, and chlorpyrifos in laboratory aquaria and outdoor macrocosms.

Dissipation processes are described for a combination of commonly used pesticides-atrazine (6-chloro-4-ethylamino-6-isopropylamino- s-triazine), metolachlor (2-chloro- N-[2-ethyl-6-methyl-phenyl]- N-[2-methoxy-1-methylethyl] acetamide), and chlorpyrifos ( O-O diethyl O-[3,5,6-trichloro-2-pyridinyl] phosphorothioate)-in a laboratory and outdoor pond systems. Dosing rates and timing were designed to duplicate those common in the mid-Atlantic Coastal Plain, USA. Treatments ranged from 2 and 2.5 mg/L to 0.2 and 0.25 mg/L respectively for atrazine and metolachlor, and chlorpyrifos was added at 1.0 and 0.1 mg/L in the aquaria and at 0.1 mg/L in the outdoor macrocosms. Chlorpyrifos disappearance was rapid in all of the systems and followed a two-phase sequence. Initial half-lives varied from 0.16 day to 0.38 day and showed similar rates in the aquaria and the outdoor systems. The second phase of the chlorpyrifis loss pattern was slower (18-20 days) in all the treatments except for the low herbicide treatment in the outdoor test, where it was 3.4 days. Compared to the outdoor system, herbicide losses were much slower in the aquaria, e.g., 150 days for atrazine and 55 days for metolachlor, and no appreciable loss of herbicide was apparent in the high-treated aquaria. In the outdoor systems, the half-lives for the low herbicide treatment were 27 days and 12 days, respectively, for atrazine and metolachlor, and 48 and 20 days, respectively for the high herbicide-treated pond. Very low levels of CIAT (6-amino-2-chloro-4-iso-propylamino- s-triazine) and CEAT (2-chloro-4-ethylamino-6-ethylamino- s-triazine), degradation products of atrazine, were observed in the outdoor studies.

Dissolved oxygen dynamics in salt marsh pools and its potential impacts on fish assemblages

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 258:223-232 (2003) - doi:10.3354/meps258223 Dissolved oxygen dynamics in salt marsh pools and its potential impacts on fish assemblages Kelly J. Smith1, Kenneth W. Able2,* 1Department of Biology, University of North Florida, 4567 St. Johns Bluff Road South, Jacksonville, Florida 32224-2661, USA 2Marine Field Station, Institute of Marine and Coastal Sciences, Rutgers University, 800 c/o 132 Great Bay Boulevard, Tuckerton, New Jersey 08087-2004, USA *Corresponding author. Email: able@imcs.rutgers.edu ABSTRACT: In order to determine the dynamics of dissolved oxygen (DO) in salt marsh pools and its effect on their respective fish assemblages, DO was measured in 5 high-salinity pools in a Spartina alterniflora marsh in southern New Jersey over ten 24 h periods, from 2 July to 22 October 1990, to determine daily and monthly fluctuations. Typically, DO peaked at approximately 16:00 h, and reached a minimum by about 05:00 h. The greatest variation occurred in mid-July, when DO ranged from over 20 ppm at midday, to 0 ppm in the early morning. From mid- to late August, DO remained at very low concentrations (<1.0 ppm) for long periods (11.7 ± 1.7 h). DO concentrations varied among marsh pools, but there was no interaction between pool and time of day. The young-of-the-year (YOY) of the dominant 5 species of fishes in these pools were tested for tolerance and behavioral responses to low DO in laboratory aquaria. Fundulus heteroclitus survived the longest at low DO, and Menidia menidia was least tolerant. Aquatic surface respiration (ASR) was the primary behavioral response to low DO for all species tested. All species, including Cyprinodon variegatus, Lucania parva, and M. beryllina, survived at DO < 0.5 ppm when they used ASR; however, when fish were denied access to the air-water interface, only F. heteroclitus was able to survive more than 1 h. All species initiated ASR at ca. 1 ppm, with the exception of M. menidia, which began ASR at 2.6 ppm and survived only at higher concentrations of DO. In summary, although the salt marsh pools showed extreme diurnal variability in DO, with rapid drops from supersaturation to anoxic conditions, all of the fish species, with the exception of M. menidia, were well adapted to survive these fluctuations. This lack of tolerance to low DO by M. menidia may seasonally limit its occurrence in marsh pools, but this is not the case for the congener M. beryllina, or the other resident fishes. KEY WORDS: Dissolved oxygen · Salt marshes · Pools · Killifishes · Silversides · Young-of-the-year Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 258. Online publication date: August 29, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Averaging Pore Statistics of Two-Dimensional Images for Predicting Permeability

Effective medium theory (EMT) was employed to estimate permeability of fine-grained estuarine sediments. X-radiographs were taken of sediment cores collected in the field and from laboratory aquaria, designed to mimic the benthic environment of an estuary. Image analysis of two-dimensional X rays provided values of pore parameters required by the EMT model, which include pore body and throat radii, pore throat length, porosity, and the interconnectivity of pores. Values of these parameters were used to quantitatively calculate permeability based upon Darcy’s law. The EMT model with an arithmetic mean for averaging pore parameters predicted permeability 1 order of magnitude higher than measured values. The harmonic mean for averaging pore parameters in the EMT model provided estimates of permeability similar to measured values.

ACTIVITY AND MICROHABITAT USE DURING INTERACTIONS AMONG FIVE SPECIES OF POND-BREEDING SALAMANDER LARVAE

We evaluated five species of the genus Ambystoma in laboratory aquaria to quantify the effect of other larvae on microhabitat use and activity. We studied microhabitat use by partitioning containers into microhabitats that either contained or lacked refuges and recorded movement to determine activity. All five species altered microhabitat preferences and activity levels when they shared tanks with larvae of most species. The smallest species (A. laterale and A. maculatum) spent the most time in the vegetated chamber, used the vegetated chamber more often, and decreased activity in the presence of potential predators. When species were paired, both species usually changed their activity and use of microhabitat in opposite directions. These behaviors may be important in maintaining coexistence among species by reducing interspecific aggression and intraguild predation.