Jefferson T. Turner

Ecology of harmful algae

Part A Harmful Algae and Their Global Distribution 1 An Introduction to Harmful Algae E. GRANELI and J.T. TURNER References 2 Molecular Taxonomy of Harmful Algae S. JANSON and P.K. HAYES 2.1 Introduction 2.2 Dinophyta (Dinoflagellates) 2.2.1 General Morphology 2.2.2 Dinophysis 2.2.3 Alexandrium 2.2.4 Protoperidinium, Prorocentrum 2.2.5 Karenia, Karlodinium, Takayama 2.2.6 Amphidinium, Cochlodinium, Gyrodinium 2.3 Cyanobacteria (Blue-Green Algae) 2.3.1 Anabaena, Aphanizomenon, Nodularia 2.3.2 Microcystis 2.3.3 Trichodesmium 2.4 Bacillariophyta (Diatoms) 2.4.1 Amphora, Pseudo-nitzschia, Nitzschia 2.5 Concluding Remarks References 3 The Biogeography of Harmful Algae N. LUNDHOLM and O. MOESTRUP 3.1 Biogeography and Species Concepts 3.1.1 Genetic Variation 3.2 Biogeographical Distribution 3.3 Distribution of Harmful Species 3.3.1 Dinoflagellates 3.3.2 Diatoms 3.3.3 Haptophytes 3.3.4 Raphidophyceans 3.3.5 Cyanobacteria References 4 Importance of Life Cycles in the Ecology of Harmful Microalgae K.A. STEIDINGER and E. GARCES 4.1 Introduction 4.2 Phases of Phytoplankton Bloom Development and Life Cycles 4.2.1 Initiation 4.2.2 Growth and Maintenance 4.2.3 Dispersal/Dissipation/Termination 4.3 Environmental Factors versus Biological Factors Affecting Transition 4.4 Status of Knowledge and Direction Needed References Part B The Ecology of Major Harmful Algae Groups 5 The Ecology of Harmful Dinoflagellates J.M. BURKHOLDER, R.V. AZANZA, and Y. SAKO 5.1 Introduction 5.2 GeneralEcology 5.2.1 Motility 5.2.2 Temperature, Light, Salinity and Turbulence 5.2.3 Nutrition: the Continuum from Auxotrophy to Parasitism 5.3 Blooms, Including Toxic Outbreaks 5.4 Human Influences 5.5 Conceptual Frameworks to Advance Understanding References 6 The Ecology of Harmful Flagellates Within Prymnesiophyceae and Raphidophyceae B. EDVARDSEN and I. IMAI 6.1 Introduction 6.2 Class Prymnesiophyceae (Division Haptophyta) 6.2.1 Taxonomy, Morphology and Life History 6.2.2 Distribution and Abundance 6.2.3 Autecology and Ecophysiology 6.2.4 Toxicity and Toxins 6.2.5 Ecological Strategies 6.3 Class Raphidophyceae (Division Heterokontophyta) 6.3.1 Taxonomy, Morphology and Life History 6.3.2 Distribution and Abundance 6.3.3 Autecology and Ecophysiology 6.3.4 Toxicity 6.3.5 Ecological Strategies References 7 The Ecology of Harmful Diatoms S.S. BATES and V.L. TRAINER 7.1 Introduction 7.2 Toxin-Producing Diatoms, Genus Pseudo-nitzschia 7.3 Domoic Acid in the Marine Food Web 7.4 Physiological Ecology of Pseudo-nitzschia spp 7.5 Molecular Tools for Studying Pseudo-nitzschia 7.6 Conclusions and Directions for Future Research References 8 Ecology of Harmful Cyanobacteria H.W. PAERL and R.S. FULTON III 8.1 Introduction 8.2 Environmental Factors Controlling CyanoHABs 8.2.1 Nutrients 8.2.2 Physical-Chemical Factors: Salinity and Turbulence 8.2.3 Salinity and Turbulence 8.3 CyanoHAB Interactions with Micro/Macroorganisms 8.4 CyanoHAB Management References 9 Brown Tides C. J. Gobler and W. G. Sunda 9.1 Background 9.2 Nutrients and Physical Factors 9

Zooplankton Fecal Pellets in Aquatic Ecosystems

A growing body of evidence suggests that fecal pellets of crustacean zooplankton may provide a mechanism by which organic and inorganic materials are packaged and translocated to the deep portions of lakes and oceans. The mechanical fragmentation of food items during zooplankton feeding may partly account for the recycling of these materials in the water column. Small pellets recycle organic matter in surface layers and larger pellets are more important in transporting organic matter to the deeper regions. The nutritional content of fecal pellets, fecal pellet membranes, zooplankton coprophagy, recycling of fecal pellet contents, and fecal pellets and pollution are discussed. (RJC)

How long does it take copepods to make eggs

Abstract During investigations of relationships between food concentrations and rates of egg production by the marine copepod Anomalocera ornata Sutcliffe, we discovered an artifact that may be common in such experiments. Although rates of egg production by individual copepods were highly variable and rates exhibited no relation to food concentration offered during experimental incubations, egg production rates of up to 338 eggs·female −1 ·day −1 were obtained with natural phytoplankton and up to 83–128 eggs female −1 ·day −1 with unialgal phytoplankton cultures. However, concurrent measurements of ingestion rates in experiments with cultures revealed that the copepods were not eating. This suggested that food used to produce eggs during experiments had been ingested in the sea prior to capture. To test this, we offered 14 C-labelled mixtures of diatoms and rotifers to five copepod species, and measured the lag period for labelled eggs to appear. Times for maximum measured values of counts per minute per egg were 9.5 h for Acartia tonsa Dana, 16.5 h for Centropages veliflcatus De Oliviera, 65.5 h for Labidocera aestiva Wheeler, 89 h for Centropages typicus Kroyer, and 91 h for A. ornata. C. typicus and A. ornata continued to produce eggs in filtered seawater for periods of 66.8 and 44.5 h, respectively. We concluded there is considerable interspecific variability in the lag period for conversion of ingested food to egg production in marine copepods, and this lag time must be known in order to interpret relationships between food and copepod egg production.

Feeding, egg production, and egg hatching success of the copepods Acartia tonsa and Temora longicornis on diets of the toxic diatom Pseudo-nitzschia multiseries and the non-toxic diatom Pseudo-nitzschia pungens

In 1987, there was an episode of shellfish poisoning in Canada with human fatalities caused by the diatom Pseudonitzschia multiseries, which produced the toxin domoic acid. In order to examine whether domoic acid in this diatom serves as a grazing deterrent for copepods, we compared feeding rates, egg production rates, egg hatching success and mortality of the calanoid copepods Acartia tonsa and Temora longicornis feeding on unialgal diets of the toxic diatom P. multiseries and the similarly-sized non-toxic diatom Pseudo-nitzschia pungens. Copepods were collected in summers of 1994, 1995 and 1996 from Shediac Bay, New Brunswick, Canada, near Prince Edward Island, the site of the 1987 episode of domoic acid shellfish poisoning. Rates of ingestion of the toxic versus the non-toxic diatom by A. tonsa and T. longicornis were similar, with only one significantly different pair of values obtained in 1994, for which A. tonsa had a higher mean rate of ingestion of the toxic than the non-toxic diatom. Thus, domoic acid did not appear to retard grazing. Analyses of copepods with high performance liquid chromatography (HPLC) revealed that copepods accumulated domoic acid when feeding on P. multiseries. Egg production rates of copepods when feeding on P. multiseries and P. pungens were very low, ranging from 0 to 2.79 eggs female−1 d−1. There did not appear to be differential egg production or egg hatching success on diets of the toxic and non-toxic diatoms. Mortality of females on the toxic diet was low, ranging from 0 to 20%, with a mean of 13%, and there was no apparent difference between mortality of copepods feeding on toxic versus non-toxic diatoms. Egg hatching success on both diets, although based on few eggs, ranged between 22% and 76%, with a mean percentage hatching of 45%. Diets of the non-toxic diatom plus natural seawater assemblages supplemented with dissolved domoic acid, revealed similar rates and percentages when compared to previous experiments. In summary, none of the variables measured indicated adverse effects on copepods feeding on the toxic compared to the non-toxic diatom.

ZOOPLANKTON FEEDING ECOLOGY - GRAZING DURING ENCLOSURE STUDIES OF PHYTOPLANKTON BLOOMS FROM THE WEST-COAST OF SWEDEN

Zooplankton feeding ecology: grazing during enclosure studies of phytoplankton blooms from the west coast of Sweden

The annual cycle of zooplankton in a Long Island estuary

Zooplankton and chlorophyll-a samples and associated hydrographic data were collected at approximately weekly intervals in the Peconic Bay estuary for most of the period between May 1978 and June 1979. Surface zooplankton samples were obtained by simultaneously-towed 73 μm- and 202 μm-mesh nets, and subsurface samples were collected with 505 μm-mesh nets. Zooplankton numbers and displacement volumes fluctuated widely throughout the year, with highest values in early spring and summer. Juvenile or adult copepods accounted for means of 90.0% and 85.0% of the animals recorded for the 202 μm- and 73 μm-net samples, respectively. The combination of Acartia tonsa and A. hudsonica adults+copepodids accounted for a mean of 81.4% of the zooplankton recorded for the 202 μm-net samples, and the combination of copepod nauplii, Acartia spp. adults+copepodids, Oithona colcarva and Parvocalanus crassirostris accounted for a mean of 82.7% of the animals recorded for the 73 μm-net samples. Copepod nauplii were the most abundant zooplankters collected in the 73 μm-net samples, and they were generally collected in higher numbers than the total number of animals in the 202 μm-net samples. During the colder months, late copepodids and adults of larger copepod species comprised greater proportions of the total zooplankton than during the warmer months when nauplii and copepodids of smaller copepod species were predominant. The ctenophore Mnemiopsis leidyi and the medusa Cyanea capillata also had periods of abundance during warmer months. Differences between numbers of larger zooplankters collected over different depth intervals or in successive replicate tows over the same depth intervals, reveal the likely effects of both vertical and horizontal patchiness. Comparisons of zooplankton numbers from the present investigation, which were obtained with relatively fine-mesh nets, with values from previous studies in adjacent waters which used coarser-mesh nets, suggest that many previous investigations have seriously underestimated the numbers of smaller zooplankters, particularly copepod nauplii.

Primary productivity and phytoplankton size fraction dominance in a temperate North Atlantic estuary

The composition, productivity, and standing crop of net (>20 μm) and nano-(<20 μm) phytoplankton of Peconic Bay, Long Island, New York was examined from June 1978 through May 1979. Nanoplankton, primarily small solitary flagellates, chlorophytes, and diatoms, dominated from May through September accounting for 88.5% of the productivity and 88.1% of the standing crop (measured as chlorophyll a). An apparent net plankton bloom began in December and continued through March. The dominant organism through most of the winter bloom was the chain-forming diatom Skeletonema costatum (Grev.) Cl. Net plankton at this time represented 66.4% of the standing crop. For both size fractions, productivity/chlorophyll a (g C per g chl a per d, integrated through the euphotic zone) was a function of light energy over the year with the exception of a few sampling dates during the post-winter bloom period. Assimilation numbers (g C per g chl a per h at saturating light intensities) were a function of temperature between 0 and 20°C. Nitrogen deficiency did not appear to be a factor in regulating phytoplankton growth rate through the euphotic zone, as ratios of 14C assimilation for dark bottles enriched with NH3 and with no enrichment exhibited no relationship to environmental dissolved inorganic nitrogen concentrations. Zooplankton grazing pressure appeared to have been an important factor in regulating the upper limit of phytoplankton biomass and in influencing size fraction dominance. Dominance of one phytoplankton size fraction over the other on any given date was not based on physiological differences between the two groups since both fractions were composed of the same species. Apparent net phytoplankton blooms (in terms of productivity and chlorophyll a) were artifacts of increased chain lengths of nanoplankton diatoms such as Skeletonema costatum, and to a lesser extent, Thalassiosira nordenskioldii Cl. and Detonula confervacea (Cl.) Gran, rather than to the dominance of large, solitary cells.

Zooplankton feeding ecology: nonselective grazing by the copepods Acartia tonsa Dana, Centropages velificatus De Oliveira, and Eucalanus pileatus Giesbrecht in the plume of the Mississippi River

Grazing on natural particulate assemblages by the copepods Acartia tonsa Dana, Centropages velificatus De Oliveira and Eucalanus pileatus Giesbrecht was examined in shipboard experiments in the Mississippi River plume (northern Gulf of Mexico continental shelf)- Copepods fed during simultaneous experiments in food-rich surface waters of the plume and in the less-food-rich waters 8–12 m below the plume. Grazing by these three copepods was generally nonselective. Ingestion and filtration rates, as well as electivity of individual phytoplankton taxa, were calculated after phytoplankton cell counts were completed from 51 experiments. Phytoplankton species were eaten primarily in proportion to their abundance, without regard to differences in cell size and/or shape. Plots of electivity vs. two different measurements of cell size (cell volume and maximum linear dimension) for each of the 51 individual experiments revealed only three cases of selective feeding. These quantitative results support previous qualitative studies of fecal pellet contents using scanning electron microscopy.

Zooplankton feeding ecology: bacterivory by metazoan microzooplankton

Bacterivory by the rotifer Brachionus plicatilis Muller, nauplii and copepodites of the copepods Centropages Kroyer sp. and Acartia tonsa Dana, and the tintinnid Favella panamensis Kofoid & Campbell was examined using fluorescently labelled bacteria (FLB) and epifluorescence microscopy. FLB were < 1 μm in diameter, and were offered at environmental concentrations (1.47−9.08 × 106 cells·ml−1). FLB were visible within rotifers, nauplii, copepodites, and tintinnids, confirming ingestion. Rotifer clearance rates (32–418 μl·animal−1·h−1) exhibited no relation with FLB concentration. In some cases rates of clearance of FLB by rotifers were different with alternative phytoplankton food (Nanochloris Naumann sp.) than in replicates with FLB alone, whereas in other cases presence of alternative food exhibited no clear effects on rates of ingestion of FLB. Clearance rates for all six naupliar stages of A. tonsa nauplii (0–320 μl·animal−1·h−1) were stage-related, with higher rates by NIII-VI nauplii than NI-II nauplii. Nauplii had higher rates of clearance of FLB in the absence of alternative phytoplankton food (Isochrysis Parke sp.). Clearance rates of FLB by a single stage of Centropages sp. nauplii, A. tonsa CI copepodites and F. panamensis (each obtained at only a single food concentration of either 1.5 or 5.0 × 106 cells·ml−1) were within the range of 85–142 μl·animal−1·h−1. These ranges were similar to those of rotifers and A. tonsa nauplii. This is the first report of FLB ingestion by metazoan marine microzooplankton. Although rotifers and ciliates might be expected to ingest small particles such as FLB using ciliary induced feeding currents, the means by which nauplii and copepodites eat FLB is less clear. We propose that they may “eat” bacteria as they “drink” to osmoregulate.

Zooplankton feeding ecology

Hjort proposed that fishery year-class fluctuations are due mainly to variable larval mortality, and that most mortality is due to early starvation. Some larvae die because they do not find enough zooplankton to eat, but others may die because zooplankton cat them. We examined predation upon eggs, yolk-sac, and/or first-feeding larvae of Atlantic menhaden (Brevoortia tyrannus), gulf menhaden (B. patronus) and spot (Leiostomus xanthurus) by adults of larger (Anomalocera ornata) and smaller (Centropages typicus) copepods. B. tyrannus eggs were too large for either copepod to grasp or ingest. A. ornata could grasp and apparently kill, but not ingest, the smaller L. xanthurus eggs, but C. typicus could not. Both yolk-sac and first-feeding B. tyrannus larvae and first feeding B. patronus larvae were grasped and completely consumed in<4 min by A. ornata. C. typicus ingested yolk-sac larvae of both fish, but not first-feeding larvae of either species. Ingestion rates by A. ornata were significantly related to prey density (ANOVA; p<0.001). Ingestion rates by C. typicus (<2 larvae copepod d-1) were much lower than those of the larger A. ornata (up to 14 larvae copepod d-1) at food concentrations of 10 to 50 larvae l-1. However, expressed as % copepod body carbon ingested copepod d-1, ration by the smaller copepod equalled or exceeded that of the larger. Since copepods and fish larvae can become concentrated together in surface windrows, copepod predation may represent a substantial source of mortality of fish larvae.