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Due to the construction of two cross-shore groynes near Waarde in the Western Scheldt estuary, the Netherlands, morphological changes in the area have occurred. A mud flat has developed between the groynes and at the tip of the groynes scour has occurred which has contributed to channel migration. Both the sand and mud fraction have contributed to this change. In this paper a process-based morphological model is presented that can reproduce most morphological changes thanks to the fact that both fractions are taken into account, as well as the interaction between sand and mud. Using the model, 5 years of morphological changes were simulated from the construction of the groynes onwards. The Brier-skill score of the erosion/sedimentation pattern is 0·35, which means that the model has significant skill and can be classified as reasonable. A regression coefficient of 0·66 is found for the observed and modelled mud content in the bed after 5 years, which means that the model can reproduce the mud content reasonably well for most locations. The model can clearly distinguish between a sand- or mud-dominated area.

Short-term experiments were conducted to examine the response of the ciliate Tia- rina fusus and the heterotrophic dinoflagellate Polykrikos kofoidii to 3 strains in the Alexandrium tamarense species complex, each with a different paralytic shellfish toxin (PST) content. Both pro- tist species fed on all 3 Alexandrium strains, but significant mortality occurred within 24 h of initial exposure to high densities of each dinoflagellate isolate. Protist mortality was not related, how- ever, to the PST content of the Alexandrium strains, indicating a different mechanism of toxicity. Exposure of T. fusus to cell-free culture filtrates or cell extracts did not cause significant ciliate mortality. In contrast, significant mortality occurred when ciliates were separated physically from a live Alexandrium sp. culture by a 10 µm nylon mesh, suggesting that the toxicity is dependent upon the viability of the Alexandrium spp. cells but does not require physical contact or ingestion. Addition of antioxidant compounds significantly increased the survival of both protist species when exposed to Alexandrium, suggesting that reactive oxygen species and/or the secondary compounds produced by ROS-induced lipid peroxidation are involved in the toxicity of Alexan- drium spp. to ciliates and heterotrophic dinoflagellates. This mechanism of toxicity is previously unknown for Alexandrium spp. and may play an important role in bloom dynamics and toxin transfer within the food web.

Nutritional insufficiency and toxicity are deleterious effects of phytoplankton on grazers. We hypothesize that toxic food is likely to have stronger evolutionary selective effects on grazers than nutritionally insufficient food. We explore this hypothesis in comparative studies of egg production and egg hatching of the copepod Acartia hudsonica challenged with both a toxic and a nutritionally insufficient alga. Experiments lasting 6 days, in which mixtures of different proportions of the suspect and a control alga were offered as food to female copepods, showed that the dinoflagellate Alexandrium fundyense, which bears paralytic shellfish toxins, was toxic to A. hudsonica. In contrast, the diatom Phaeodactylum tricornutum was nutritionally insufficient to A. hudsonica. In another set of experiments, the effects of A. fundyense and P. tricornutum, respectively, as sole foods on egg production and egg hatching success of two geographically separated populations (Maine and Connecticut) of the copepod A. hudsonica were examined in common-environment experiments, after being raised under identical conditions for two generations. The location in Maine regularly experiences toxic blooms of Alexandrium sp. whereas the location in Connecticut does not. During a 6-day period, A. fundyense reduced the egg production rates of the Connecticut copepod population, but not of the Maine population. In contrast, the diatom P. tricornutum reduced the egg production of both populations. These results of this study are consistent with the hypothesis of local adaptation to toxic food, but not to nutritionally insufficient food.

Phenotypic tolerance of individual copepods to paralytic shellfish toxins (PSTs), as determined by fecundity, has recently been reported. In the present study, we tested whether similar phenotypic tolerance related to ingestion also exists. In short-term feeding assays, ingestion rates of individual females of the copepod Acartia hudsonica were measured on a sole diet of toxic Alexandrium fundyense as well as on a sole diet of nontoxic Alexandrium tamarense . When copepods fed on A. fundyense , the frequency distribution of ingestion rates was polymodal, consistent with the hypothesis of levels of phenotypic tolerance associated with toxin ingestion. Four distinct groups of ingestion rates on toxic algae were observed. Mean rates ranged from near zero to more than 100 cells copepod −1 h −1 . In contrast, when the same individuals fed on the nontoxic A. tamarense diet, the polymodal distribution of ingestion rates was not apparent. Furthermore, group-specific mean ingestion rates, for two ingestion-defined groups, were always significantly greater on the toxic diet than they were on the nontoxic diet. These results support the hypothesis that discrete groups of grazer ingestion of toxic A. fundyense are related to PST tolerance.

In common-environment experiments, we measured the uptake, accumulation, retention, transformation and depuration of paralytic shellfish toxins (PSTs) of the dinoflagellate Alexandrium fundyense in adult females of two geographically separated populations (Maine and New Jersey, USA) of the copepod Acartia hudsonica. These populations were previously shown to differ in their history of exposure to Alexandrium blooms, and in their degree of adaptation to this dinoflagellate. Toxin accumulation was measured at several times in incubations lasting up to 72 h. Toxin depuration was assessed after a 60 h incubation of females with toxic A. fundyense and subsequent 60 h incubation in a sole diet of the non-toxic green flagellate Tetraselmis sp. As previously observed, the Maine population had significantly higher toxin ingestion rates. By contrast, both toxin accumulation (up to ∼2.5 ng STX eq. female −1 ) and the depuration rate (∼0.73 d −1 ) were not significantly different between populations. Hence, faster depuration is ruled out as a tolerance mechanism in the Maine population. Some toxin transformation during both accumulation and depuration was evident in both populations. However, differential toxin transformation does not appear to be a tolerance mechanism either. In contrast to these results, toxin retention (ratio of accumulation/cumulative ingestion) was significantly lower in the Maine population. The retentions of gonyautoxin 3 (GTX3) and of two of the most potent toxins, neosaxitoxin (NEO) and saxitoxin (STX), were also significantly lower in that population. At steady state, toxin absorption efficiency was estimated to be 6% for the Maine population and 9% for the New Jersey population. These results suggest that lower toxin absorption is a possible tolerance mechanism for the Maine population. The results of the present study also suggest that copepod adaptation to toxic dinoflagellates does not necessarily lead to higher toxin transfer up the food web.

The refeeding syndrome is a potentially fatal condition that affects multiple organ systems. It is the consequence of fluid and electrolyte shifts that may occur in a malnourished patient following the introduction of nutrition therapy. The most prominent characteristic is hypophosphataemia. Although hyperammonaemia is usually seen in decompensated liver cirrhosis or acute liver failure, it may occur in other settings. We report a clinical case of prolonged and severe encephalopathy accompanied by hypophosphataemia and hyperammonaemia in a 59-year-old woman with no preexisting liver disease, urea cycle defects or portosystemic shunting. We suggest that these biochemical abnormalities were caused by uncontrolled refeeding and that the clinical picture was consistent with refeeding encephalopathy.

Deficientie van guanidinoacetaatmethyltransferase (GAMT) is een relatief recent ontdekte aangeboren stofwisselingsziekte in de creatinestofwisseling. Patienten presenteren zich met achterstand in ontwikkeling, epilepsie en/of een bewegingsstoornis. Onderzoek naar de ziekte is eenvoudig uit te voeren door metabool onderzoek in plasma en urine in een laboratorium dat gespecialiseerd is in metabole ziekten.Wanneer behandeling uitblijft, leidt de ziekte tot progressieve hersenschade, terwijl dit met vroegtijdige behandeling voorkomen kan worden. Aan de hand van de ziektegeschiedenis van een patient wordt ingegaan op de klinische symptomen, diagnostiek en behandeling van deze ziekte

We used laboratory food chains to experimentally explore the independent and combined effects of omnivory and food quality on planktonic trophic interactions. Omnivory is predicted to dampen indirect (trophic cascade) interactions, whereas availability of a low-quality diet, here defined as predator-prey elemental stoichiometric imbalance, should strengthen both direct (grazing and predation) and indirect interactions. Food chains were constructed with a copepod, Acartia tonsa, an aloricate ciliate, Strombidinopsis sp., and two centric diatoms of different size, Thalassiosira weissflogii (larger) and Thalassiosira pseudonana (smaller). Comparing results between food chains with two (copepod and diatoms or ciliate and diatoms) and three (copepod, ciliate, and diatoms) trophic levels tested omnivory effects. Offering grazers phytoplankton grown under nitrogen-replete and nitrogenlimited conditions tested stoichiometric imbalance effects. Carbon ingestion increased by 25% for the copepod and 160% for the ciliate on the nitrogen-limited relative to the nitrogen-replete diatom, demonstrating considerable compensatory feeding by both grazers. On a mixed diet comprised of the nitrogen-limited large diatom and the nitrogen-replete small diatom, the copepod continued to engage in compensatory feeding, but the ciliate did not. Cascading indirect effects of the copepod on phytoplankton via the ciliate were minimal. The decrease in phytoplankton due to direct grazing by the copepod was much greater than any indirect increase resulting from reduced ciliate grazing pressure. Omnivory and compensatory feeding were stronger than positive prey selection for the N-replete intermediate grazer, thus weakening cascading indirect effects of the top predator on phytoplankton.

In this study we hypothesized that the sexes of the copepod Acartia hudsonica experience different mortalities when exposed to the toxic dinoflagellate Alexandrium fundyense. In laboratory experiments, we manipulated toxin dose and measured sex-specific mortality. We also used a split-family design to determine whether there were genetic influences on sex determination, and therefore on sex ratio. When the dose of the toxic alga was high (25% of diet by carbon content), population mortality was high, and the fraction of males surviving to adulthood was low (20-30% of the adult population). No such effect was observed when A. fundyense comprised only 10% of the diet. Adult male copepods were also more susceptible to the toxic alga, though prior selection for resistance to toxins also had an effect on mortality. No genetic variation for sex ratio was detected in the split-family experiment. Males of A. hudsonica are more sensitive to the toxins of A. fundyense than are females. Resistance may be sex-linked, and copepod populations exposed to a bloom of toxic Alexandrium sp. may experience shifts in sex ratios away from males and toward females. Differential mortality and skewed sex ratios are feedback mechanisms potentially affecting both the population dynamics of grazers and the development of toxic algal blooms.

The functional and numerical responses of grazers are key pieces of information in predicting and modeling predator‐prey interactions.Ithas beendemonstrated thatexposure totoxicalgae canlead toevolvedresistancein grazerpopulations.However,the influence of resistance on the functional and numerical response of grazers has not been studied to date. Here, we compared the functional and numerical responses of populations of the copepod Acartia hudsonica that vary in their degree of resistance to the toxic dinoflagellate Alexandrium tamarense. In common environment experiments carried out after populations had been grown under identical conditions for several generations, female copepods were offered solutions containing different concentrations of either toxic A. tamarense or the non-toxic green flagellate Tetraselmis sp. ranging from � 25 to 500 mgC L � 1 , and ingestion and egg production rates were measured. Throughout most of the range of concentrations of the toxic diet, copepod populations that had been historically exposed to toxic blooms of Alexandrium exhibited significantly higher ingestion and egg production rates than populations that had little or no exposure to these blooms. In contrast, there were no significant differences between populations in ingestion or egg production for the non-toxic diet. Hence, the between population differences in functional and numerical response to A. tamarense were indeed related to resistance. We suggest that the effect of grazer toxin resistance should be incorporated in models of predator and toxic prey interactions. The potential effects of grazer toxin resistance in the development and control of Alexandrium blooms are illustrated here with a simple simulation exercise. # 2007 Elsevier B.V. All rights reserved.

Egg-carrying pelagic copepods are characterized by low reproductive growth rates. It has been suggested that this is due to relatively high mortality rate in adult females, relative to broadcast spawning copepods. The poecilostomatoid copepod Sapphirina angusta , a ubiquitous member of pelagic zooplankton communities, seems to be an exception to this rule. We studied egg production of S. angusta on the Southern Brazilian Bight. In five separate experiments, egg clutch size was measured in 15 to 25 individual females followed for approximately 5 days in each experiment. The mean time to produce a clutch was ∼ 2 days. Egg hatching success was > 80% and independent of clutch size or egg production rate. Clutch size ranged from 9 to > 1000 eggs female − 1 during the study. The mean egg production rate was estimated from clutch size and the inter-spawning period. The mean and median egg production rate were essentially similar and ranged from 155 to 218 eggs female − 1 d − 1 among experiments, with a grand mean of 186 eggs female − 1 d − 1 . This is the highest observed egg production rate in an egg-carrying copepod. Based on female and egg body mass, the egg production rate represents a growth rate of ∼ 0.45 d − 1 , among the highest in all marine copepods. We hypothesize that two evolutionary factors that select for high fecundity are responsible for the extremely high egg production rate of S. angusta : 1) The symbiosis of Sapphirina and their host salps, which relaxes female mortality; 2) The parasitoid (both parasitic and predatory) behavior of Sapphirina leading to death of their salp host, which causes high mortality in Sapphirina juveniles while in between highly patchy hosts.

We document for the first time toxin-resistant reproductive phenotypes of copepods and we describe a novel procedure to identify these phenotypes. Individual copepods of the species Acartia hudsonica were raised on two diets: a standard nontoxic diet and a diet containing the toxic dinoflagellate Alexandrium fundyense, both offered at nonlimiting concentrations. Resistant individuals were defined as those that survived on the toxic diet. We examined several life-history characters including survivorship, age at metamorphosis, age at maturity, fecundity, and fitness. During this study, we discovered five resistance-related reproductive phenotypes that appeared as discrete classes in a frequency distribution of fecundity. After grouping the data according to these phenotypes, we calculated the fitness of each phenotype on each diet. We also calculated the cost and advantage associated with resistance. On the standard diet, one phenotype had 46% lower fitness than the phenotype with the highest fitness, indicating that possessing resistance alleles can carry a substantial cost. A different phenotype showed maximum relative fitness on the toxic diet and reduced relative fitness on the standard diet. From these results, we argue that resistance is conferred by a simple genetic system showing heterozygote advantage and leading to a polymorphism for resistance. Such a polymorphism will prevent the fixation of resistance alleles in natural populations. It may also confound the interpretation of typical experiments that measure average population responses.

We thank Dr Tasci et al.1 for their interest in our case report 'Refeeding encephalopathy in a patient with severe hypophosphataemia and hyperammonaemia'2 and for drawing our attention to the importance of including acid–base status in the evaluation of the comatose malnourished patient. In their letter, Dr Tasci et al. point to a number of relevant issues.

We measured grazing by herbivorous zooplankton ( 80% of phytoplankton production. A comparison of incubations with and without added inorganic nutrients showed no consistent stimulation of phytoplankton growth (slope of enriched versus unenriched treatments not significantly different from 1). Estimates from microscopic counts of heterotrophic organisms >10 μm indicated that copepod nauplii comprised the largest share of the microzooplankton biomass (mean 62.4 ± 5.8% SE). Grazing estimates were not correlated with microzooplankton biomass, whether or not nauplii were included, suggesting that most of the grazing was done by nano-sized zooplankton.

With few exceptions, the evolutionary consequences of harmful algae to grazers in aquatic systems remain unexplored. To examine both the ecological and evolutionary consequences of harmful algae on marine zooplankton, we used a two-fold approach. In the first approach, we examined the life history responses of two geographically separate Acartia hudsonica (Copepoda: Calanoida) populations reared on diets containing the toxic dinoflagellate Alexandrium fundyense. One copepod population was from a region, Casco Bay, Maine, USA, that has experienced recurrent blooms of highly toxic Alexandrium spp. for decades; whereas the other population from Great Bay, New Jersey, USA, has never been exposed to toxic Alexandrium blooms. The life history experiment demonstrated that when the copepod population from New Jersey was reared on a diet containing toxic A. fundyense it exhibited lower somatic growth, size at maturity, egg production and survival than the same population reared on a diet without toxic A. fundyense. In contrast, toxic A. fundyense did not affect the life-history traits of the Maine population. Fitness, finite population growth rate (k), was significantly reduced in the New Jersey population, but not in the Maine population. These results are consistent with the hypothesis of local adaptation (resistance) of the historically exposed copepod population to the toxic dinoflagellate. In the second approach, we further tested the resistance hypothesis with a laboratory genetic selection experiment with the na€ � ve New Jersey copepod population exposed to a diet containing toxic A. fundyense. This experiment demonstrated that the ingestion and egg production of adult females of na€ � ve copepods fed A. fundyense improved after three generations of being reared on a diet containing the toxic dinoflagellate. The results of the present study have important implications for understanding how grazer populations may respond to the introduction of toxic algae to their environment, and suggest that grazer resistance may be a feedback mechanism that may lead to bloom control.

This study tested whether the dinoflagellate Prorocentrum minimum is nutritionally insufficient or toxic to the copepod Acartia tonsa. Experiments were carried out with adult female A. tonsa and the P. minimum clone Exuv, both isolated from Long Island Sound. Initially, the functional and numerical responses of A. tonsa feeding on exponentially growing P. minimum cells were characterized. These experiments revealed that A. tonsa readily ingested P. minimum cells, up to the equivalent of 200% of body carbon day 1 , but egg production was relatively low, with a maximum egg production rate of 22% of body carbon day 1 . Hence, the egg production efficiency (egg carbon produced versus cell carbon ingested) was low (10%). In a separate experiment, ingestion and egg production rates were measured as a function of food concentration with cells in different growth stages (early-exponential, late-exponential/early-stationary, and late-stationary growth phase) to simulate conditions during a bloom. There was no indication that cells in the stationary phase resulted in lower ingestion or egg production rates relative to actively growing cells. Egg hatching success remained high (>80%) and independent of the cell growth phase. In a third experiment specifically designed to test the hypothesis that P. minimum is toxic, ingestion, egg production and egg hatching success were measured when females were fed mixtures of P. minimum and the diatom Thalassiosira weissflogii, but in which total food concentration was held constant and the proportion of P. minimum in the mixed diet varied. A. tonsa readily ingested P. minimum when it was offered in the mixed diet, with no detrimental effects on egg production or egg hatching observed. Supplementing P. minimum with T. weissflogii increased both the egg production rate and the egg production efficiency. It is concluded that P. minimum is nutritionally insufficient, but not toxic to A. tonsa. Finally, it is estimated that in the field grazing by A. tonsa is approximately equivalent to 30% of the maximum daily growth rate of P. minimum. Hence, copepod grazing cannot be ignored in field and modeling studies of the population dynamics of P. minimum. # 2004 Elsevier B.V. All rights reserved.

We describe a new method to isolate and concentrate transparent exopolymeric particles (TEP), either naturally occurring or produced by phytoplankton in cultures. The principles of this method are to use TEP-sticking properties coupled with magnetic properties of paramagnetic microspheres to magnetically and selectively concentrate TEP. First, we studied the formation of mixed aggregates of TEP and 1-µm microspheres using the bubbling method. TEP precursors were obtained from diatom cultures and from natural seawater. Mixed aggregates of TEP-microspheres were efficiently formed—all TEP formed were associated with microspheres, and no clusters of microspheres alone were observed. The number of attached microspheres scaled with TEP size raised to an exponent of 1.53. The second step was to combine TEP with paramagnetic microspheres and isolate and concentrate the TEP by flowing out the solution containing mixed aggregates inside a strong magnetic field. About 90% of the magnetically labeled TEP were trapped inside the magnetic field. TEP volume concentration measured inside the magnetic field after isolation was about 5 times the initial TEP volume concentration. However, the predicted concentration factor, estimated from the relationship between number of attached microspheres versus TEP size, and the TEP size spectra in the initial solution was ~9. This suggests that TEP observed after isolation inside the magnetic field may be compacted and/or that a fraction of the TEP pool inside the magnetic field may remain glued to the inner walls of the culture flask and, thus, the observed TEP size spectra could be underestimated.

We measured in laboratory experiments the ingestion, egg production and egg hatching rates of female Temora longicornis as a function of diet. The diets consisted of a diatom (Thalassiosira weissflogii), an autotrophic dinoflagellate (Heterocapsa triquetra), and a bacterivorous ciliate (Uronema sp.) given as sole foods, or combinations of these single-food items: diatom+dinoflagellate, diatom+ciliate, dinoflagellate+ciliate, and diatom+ciliate+dinoflagellate. For the three single-item diets, the functional response was similar; i.e., ingestion rate increased linearly with food concentration (food range: ∼25 to ∼600 μg C l−1). When all diets were considered, maximum daily carbon ration (∼70% of body weight) was independent of food type. However, the maximum daily egg production rate (12% of body carbon) was obtained with the diatom diet. For all diets, both ingestion and egg production rates increased with food concentration. Ingestion and egg production rates were affected differently by the interaction of food concentration and food type: at low food concentrations, ingestion rates were highest on diets containing the diatom. At high food concentrations, egg production rates were highest on the two phytoplankter diets and their combination. The presence of the ciliate in the diet did not enhance ingestion rate or egg production. Mixed-food diets did not enhance egg production relative to single-food diets. Hence, dietary diversity did not appear to be particularly advantageous for reproduction. Carbon-specific egg production efficiency (EPE; egg production/ingestion) was independent of food concentration and type, and equaled 9%. Egg hatching success was low (mean

Fecal pellets were produced by Acartia tonsa fed 14 C-labeled diatom, cryptophyte, and dinoflagellate diets, and were incubated in 1.2 μm-filtered Long Island Sound seawater. Based on the 14 C label, the decrease in fpOC (fecal pellet organic carbon), the release and fate of dissolved organic carbon (DOC) and particulate organic carbon (POC), as well as bacterial production and enzymatic activity, were followed over a 96 h period. fpOC decreased by 9, 14, and 19% d -1 in diatom, cryptophyte, and dinoflagellate pellets, respectively. There was a fast, possibly passive, leakage of DOC from pellets from all 3 diets within a few hours after egestion, which may not have been utilized by attached bacteria. Bacterial production rates were 17, 12, and 31 pg C pellet -1 h -1 , on diatom, cryptophyte, and dinoflagellate pellets, respectively. These were 5 orders of magnitude higher than production rates of free-living bacteria, indicating that copepod fecal pellets are hot spots of pelagic microbial production. The high production was caused primarily by high initial bacterial abundances. Accordingly, production and growth were entirely uncoupled in diatom pellets. There were no increases in abundance of attached bacteria on any of the 3 diets, indicating that the produced bacterial cells were released from the fecal pellets. Attached bacteria had a higher ectoenzymatic activity than free-living bacteria, but their production and ectoenzymatic activity were uncoupled and they only assimilated a minor fraction of the released DOC. DOC was therefore released favoring free-living microbes. The chitinase activity, which increased several-fold, was coupled to the production of attached bacteria; thus, chitin may play an important role in bacterial production on copepod fecal pellets.

Reduced grazing on harmful algal bloom species has been attributed to both the feed- ing deterrence and toxicity of the algae. Both toxic and deterrent effects of dinoflagellates of the genus Alexandrium, which contain toxins that cause paralytic shellfish poisoning, have been re- ported on different copepod species. We examined how toxin-containing Alexandrium fundyense affected ingestion rates of 2 geographically distinct Acartia hudsonica (Copepoda: Calanoida) popu- lations over short timescales. The copepod population from Great Bay, New Jersey, has never been exposed to blooms of toxic A. fundyense, whereas the population from Casco Bay, Maine, has expe- rienced regular blooms of the highly toxic dinoflagellate for decades. Our goals were to examine the mechanisms by which toxin-containing Alexandrium reduced the ingestion rates of copepods and determine whether the mechanisms were related to the exposure history of copepod populations. Copepods were fed, for 48 h durations, sole diets of toxin-containing A. fundyense, non-toxin con- taining Alexandrium tamarense and the green flagellate Tetraselmis sp. (not known to have toxic effects) and different mixtures of each (70% Alexandrium/30% Tetraselmis sp., 40/60, 20/80). Changes in ingestion rates over time were determined by measuring ingestion at different time inter- vals (3, 6, 12, 24, 48 h) over the 48 h period using 3 h incubations. The naive copepods from New Jer- sey initially ingested toxin-containing A. fundyense, in both sole and mixed diets, at high rates fol- lowed by decreases in ingestion over time. By 24 h, their total ingestion rates were near zero. The decreases in ingestion rates, which were not due to prey selection, were also accompanied by reduced respiration rates. In contrast, none of these effects were observed when the New Jersey copepods fed on non-toxic A. tamarense. Additionally, feeding rates of historically exposed copepods from Maine were not affected by the toxin-containing A. fundyense diets. These observations are consistent with the hypothesis that toxic A. fundyense physiologically incapacitated the copepods from New Jersey but not those from Maine. Such toxic effects, as opposed to deterrence effects, can have profound implications on the grazers' ability to control harmful algal blooms.

Negative effects of prey species on consumers could be due to deterrence, nutritional insufficiency, or toxicity of the prey. These effects can be discerned in experiments in which the suspect prey is offered to the consumers in a food mixture containing another prey item that is not toxic and in which the ingestion rates on the prey and the grazers’ responses (e.g., egg production) are measured. We used this framework to determine whether several algae that have been reported to have harmful effects on grazers (Prorocentrum minimum, low- and high-toxin Alexandrium sp., Heterosigma carterae, Thalassiosira rotula, and Phaeodactylum tricornutum ) are toxic to females of the calanoid copepod Acartia tonsa. Ingestion, egg production, and egg-hatching rates were measured for A. tonsa offered sole diets of the suspect alga and mixed diets containing the suspect alga and a control alga (the green flagellate Tetraselmis sp.) at an ecologically relevant concentration (250 m gCL 21 ) and duration (3 d). With the exception of the Alexandrium strain with the high-toxin content (16.3 pgSaxitoxin [pgSTX] equivalents cell 21 ), none of the diets studied can be considered toxic. The high-toxin Alexandriumreduced A. tonsa’s total ingestion rate, and thus egg production, as the proportion of Alexandrium increased in the diet. A. tonsa exhibited significantly reduced ingestion and egg production rates when feeding on sole food diets of H. carterae and P. tricornutum relative to the mixed food diets. However, a comparison of ingestion rates among the diet mixtures revealed that H. carterae and P. tricornutum acted as feeding deterrents when provided as sole foods. These results stress the importance of using mixed food diets when examining putative toxic effects of preys on consumers. Reports of putatively harmful effects of phytoplankton on grazers ranging from feeding inhibition and physiological incapacitation to reductions in egg production and hatching rates are common (reviewed in Turner and Tester 1997). The broader ecological significance of these effects depends on whether they are severe enough to reduce secondary production or the grazers’ impact on algal population growth. Many studies dealing with harmful effects of phytoplankton on grazers have focused only on feeding activity, which has been found to be reduced by some phytoplankters (Ives 1987; Uye and Takamatsu 1990; Teegarden 1999). Other studies have focused on the effects on egg production and hatching rates without measuring ingestion rates (Ianora and Poulet 1993; Laabir et al. 1995; Uye 1996; Ban et al. 1997). These limitations hinder our ability to evaluate fully and predict the ecological effects of putatively harmful algae in natural systems. The harmful nature of phytoplankters is typically assumed to be due to their toxicity. Determining phytoplankton toxicity is straightforward when the effects are lethal, which is typically not the case. Moreover, a negative effect of a phytoplankter on a grazer relative to some other diet—such as

Previous studies have shown that the two green algae Tetraselmis sp. (Prasinophyceae) and Dunaliella tertiolecta (Chlorophyceae) induce high and low egg production rates in Acartia tonsa. The primary goal of the present study was to investigate if this is attributable to differences in the specific dynamic action (SDA) of the two diets. Secondly, we wanted to investigate if any qualitative differences in the incorporation of nutritional constituents from the two diets are influencing SDA. The functional response of ingestion was very different with the two diets. Ingestion of T impellucida was relatively high even at low food concentrations with a maximum of 19 mug C ind(-1) day(-1). The functional response was more clearly sigmoidal on D. tertiolecta with a maximum of 7.3 mug C ind (1) day(-1). The higher ingestion rate of T impellucida also induced higher respiration rates. Maximum respiration rates were 3.0 nl O-2 ind (1) min (1) on T. impellucida and 1.5 nl O-2 ind (1) min(-1) on D. tertiolecta. This created significantly different SDA coefficients: 0.19 on T impellucida and 0.06 on D. tertiolecta, which implies that the magnitude of SDA is strongly influenced by the composition of the diet. The incorporation of carbon into lipids was significantly higher on D. tertiolecta. However, because of lack of longer chain fatty acids in D. tertiolecta the copepods did not benefit from this. Thus, the proportion of carbon allocated to egg lipids was much lower than when feeding on T. impellucida. Acartia tonsa incorporated relatively more carbon into proteins when feeding on T. impellucida than on D. tertiolecta. Since protein synthesis is energetically very demanding this is probably the reason for the higher SDA coefficient in those feeding on T. impellucida.

Blooms of the dinoflagellate Alexandriumspp. increase in their frequency, toxicity and historical presence with increasing latitude from New Jersey (USA) to the Gaspe peninsula (Canada). Biogeographic variation in these blooms results in differential exposure of geographically separate copepod populations to toxic Alexandrium. We hypothesize that the ability of copepods to feed and reproduce on toxic Alexandriumshould be higher in copepods from regions that are frequently exposed to toxic Alexandriumblooms. We tested this hypothesis with factorial common environment experiments in which female adults of the copepod Acartia hudsonicafrom five separate populations ranging from New Jersey to New Brunswick were fed toxic and non-toxic strains of Alexandrium, and the non-toxic flagellate Tetraselmis sp. Consistent with the hypothesis, when fed toxic Alexandriumwe observed significantly higher ingestion and egg production rates in the copepods historically exposed to toxic Alexandriumblooms relative to copepods from regions in which Alexandriumis rare or absent. Such differences among copepod populations were not observed when copepods were fed non-toxic Alexandrium or Tetraselmis sp. These results were also supported by assays in which copepods from populations both historically exposed and na¨ ove to toxic Alexandrium blooms were fed mixtures of toxic Alexandrium and Tetraselmis sp. Two-week long experiments demonstrated that when

The relationship between the rates of ingestion and defecation of the calanoid copepod Acartia tonsa was examined in laboratory experiments with different diets: the diatom Thalassiosira weissflogii, the autotrophic dinoflagellate Prorocentrum minimum, the heterotrophic dinoflagellate Oxyrrhis sp., the flagellate Dunaliella tertiolecta, and the bacterivorous scuticociliate Uronema sp. Experiments were run typically using between 6 and 8 concentrations ranging from 10 to 1150 µg C l -1 . Both diet and food concentration had significant effects on ingestion rate, pellet pro- duction rates and pellet volume. Ingestion and pellet production rates increased curvilinearly with food concentration. Copepods achieved the highest pellet production rates, the largest pellets and the shortest estimated gut passage times with the diatom diet. For all diets, gut passage time decreased with food concentration in the range 0 to ca. 250 µg C l -1 , but little thereafter. In addition, for all diets, but most obviously in the case of the diatom, pellet volume increased curvilinearly with food concentration. Maximum pellet volume was achieved at food concentrations ranging from 50 to 150 µg C l -1 . The defecation and ingestion rates were best correlated when the copepods fed on the diatom and the autotrophic dinoflagellate. Likewise, a decrease in estimated assimilation efficiency with increasing food concentration was apparent only for these 2 diets. This latter pattern is primar- ily due to an increase in pellet production rate, instead of pellet volume, relative to ingestion rate at the high food concentrations. We conclude that a diatom diet is the most likely one to result in attrib- utes that enhance zooplankton-mediated export flux: high fecal pellet production rates, large pellet size and relatively low assimilation efficiency.

Zooplankton biomass and rates of ingestion, egestion and production in the equatorial Pacific Ocean along 140°W and 180° exhibit maximum values in the High-Nutrient Low-Chlorophyll (HNLC) zone associated with equatorial upwelling (5°S–5°N) as compared to the more oligotrophic regions to the north and south. Zooplankton biomass and rates are not usually highest on the equator, but increase “downstream” of the upwelling center as the zooplankton populations exhibit a delayed response to enhanced phytoplankton production. The vertical distribution of zooplankton biomass in the equatorial HNLC area tends to be concentrated in surface waters and is more uniform with depth in oligotrophic regions to the north and south of the equatorial upwelling zone. In general, the amount of mesozooplankton (>200 μm) carbon biomass is approximately 25% of estimated phytoplankton biomass and 30% of bacterial biomass in the HNLC area of the equatorial Pacific Ocean. Zooplankton grazing on phytoplankton is low in the equatorial Pacific Ocean, generally −1 for 64–200 μm zooplankton to 0.08 d −1 for 1000–2000 μm zooplankton. Thus, the numerical and functional response of equatorial zooplankton to increases in phytoplankton production are more rapid than normally occurs in sub-tropical and temperate waters. Potential zooplankton fecal pellet production, estimated from metabolic demand, is approximately 1.6 times the estimated gravitational carbon flux at 150 m in the zone of equatorial upwelling (5°S–5°N) and 1.1 times the export flux in the more oligotrophic regions to the north and south. The active flux of carbon by diel migrant zooplankton in the HNLC zone is a minor fraction of the gravitational flux (2% at 140°W, 4% at 180°) but increases in the more oligotrophic regions to the north and south where there is a deeper mixed layer and a greater relative proportion of diel migrant zooplankton.

The maximum egg mortality that a population can afford if it is not to wane, here labelled the affordable egg mortality, can be estimated from knowledge of life history traits, i.e. fecundity, development time, egg hatching time and post-egg mortality. Examination of changes in the affordable egg mortality with variations in the life history traits yields two main conclusions: when development time is short, the affordable egg mortality is maximized by reducing the egg hatching time, instead of by maximizing fecundity In contrast, when development time is long, or when post-egg mortality is high, the affordable egg mortality is maximized by a combination of low egg hatching time and very high fecundity, or by increasing the egg hatching time. For a growing population, the realized egg mortality should always be less than the affordable mortality. This condition can be exploited to check the validity of measured mortality coefficients, and is illustrated with two examples from published field studies on marine copepods. These examples reveal that for populations in temperate environments that typically display growth in the winter and spring months, high egg losses (» 1 day -1 ) cannot be sustained unless recruits are supplied from outside the population.

The amount of particulate organic carbon (POC) formed annually via the scavenging of dissolved organic carbon (DOC) by bubbles is calculated to be 1.9 Gt C yr−1. In arriving at this estimate use was made of (1) published descriptions of the bubble spectrum associated with the alpha plumes beneath spilling wave crests, (2) the published relationship of stage A whitecap coverage to wind speed, (3) data on the scale depth of alpha plumes and on the rise velocity of bubbles coated with organic film, (4) published bubble scavenging efficiencies, and (5) recorded concentrations of DOC in oceanic surface waters. This rate of DOC scavenging by bubbles represents a 1.7% yr−1 turnover of the global oceanic DOC pool, and each year produces an amount of POC equal to 17% of the POC pool in the uppermost 300 m of the ocean. Bubble scavenging turns over the DOC present in the shallow layer of bubble influence once every 67 days. Moreover, within the depth of influence of large bubbles (uppermost 1.4 m of the water column), bubble scavenging represents an annual threefold turnover of the DOC pool and a POC production equivalent to thirtyfold of the POC pool. It is noted that the amount of DOC transformed into POC each year via bubble scavenging is equal to the amount of carbon present in the carbon dioxide estimated to be absorbed by the ocean each year from the atmosphere.

DMSP-consuming bacteria (DCB) were recovered from the body and fecal pellets of the copepod Acartia tonsa (Dana). The most probable number of DCB associated with starved A. tonsa was 9.2×10 2 cells copepod −1 . The abundance of DCB recovered from the copepod body increased to 1.6–2.8×10 4 after the copepod fed on DMSP-containing alga. DCB abundance associated with fecal pellets averaged 1.2×10 4 cells pellet −1 . In enrichment cultures, the DCB grew with a doubling time of 1.1–2.9 days, and consumed DMSP at a rate of 4.5–7.5 fmol cell −1 day −1 . The apparent DMSP-to-DMS conversion efficiency was 25–41% for DCB from copepod body, and 99% for DCB from fecal pellets. Our study demonstrated that copepods and their fecal pellets may harbour dense populations of DCB, and that the copepod–bacteria coupling represents a novel mechanism for DMSP consumption in the water column.

Recent papers have reported that certain marine diatoms are deleterious to copepod egg production and hatching. Diatom harmful effects can result from 2 different mechanisms: diet- induced maternal effects and external effects. We conducted 5 separate egg incubation experiments to test if phytoplankton exudates (an external effect) were harmful to copepod eggs. Exudates pro- duced by 3 reportedly toxic diatoms, plus 2 non-diatom species, had no effects on egg hatching in the copepod Acartia tonsa. Thus, phytoplankton exudates are not likely to inhibit egg hatching. A sea- sonal relationship was observed between egg production and egg hatching of A. tonsa such that high egg production rate resulted in high egg hatching success (80 to 100%), but low egg production rate resulted in highly variable egg hatching success (0 to 90%).

Copepods contain dimethylsulfoniopropionate (DMSP) in their tissues in addition to the DMSP in their gut contents and therefore constitute an additional pool of DMSP in the ocean. In the estuarine copepod Temora longicornis Muller, this dynamic pool of DMSP is reduced when external salinity decreases. In the present study the mechanism(s) used by T. longicornis to adjust its DMSP content were examined. Four possible mechanisms were tested in experiments conducted between July 1997 and May 1999: (1) DMSP cleavage, (2) demethylation, (3) conversion to methionine, and (4) release from the body. Tissue extracts of T. longicornis did not exhibit the ability to cleave or demethylate DMSP. In incubation experiments, when external salinity decreased, T. longicornis individuals reduced their DMSP content without increasing their methionine content. The total amount of DMSP in the incubation vials was conserved regardless of salinity. The copepods retained most of the DMSP in their tissues in 30‰ water, but when salinity was reduced to 20‰, the copepods released 41 to 55% of their body DMSP to the surrounding medium; 89 to 91% of the total DMSP was recovered. This suggests that estuarine copepods represent a reservoir of DMSP, which is released as dissolved DMSP upon salinity decline. Therefore, while osmoregulation by these copepods may have little impact on the chemical properties of DMSP, it will affect the partitioning of DMSP between particulate and dissolved phases in the water column.

We studied the seasonal distribution of dimethylsulfoniopropionate (DMSP) among ses- ton, dissolved matter and zooplankton along a transect in eastern Long Island Sound. The seston DMSP concentration (1 to 52 nM) was comparable to that reported for some estuaries. Most of the ses- ton DMSP was derived from particles

The main goal of this study was to assess the effects of algal diets and water salinity on the bodily content of dimethylsulfoniopropionate (DMSP) in estuarine copepods. In laboratory experiments, Temora longicornis contained more DMSP when fed DMSP-rich Tetraselmis impellucida (prasinophyte) than when fed DMSP-poor Dunaliella tertiolecta (chlorophyte). The DMSP content of T longicornis after gut clearance was curvilinearly related to the ingestion rate. These observations suggest that the copepods incorporated the dietary source of DMSP into their body tissue. On the same diet, T. longicornis contained more DMSP at higher salinity, indicating an osmoregulatory function of DMSP. However, DMSP appears to be a minor osmolyte compared with free amino acids. The DMSP content of T. longicornis decreased faster in response to a decrease in salinity than it increased with an increase in salinity, implicating separate mechanisms for accumulation and removal of DMSP in the copepod. We also measured the bodily content of DMSP from field-collected animals. Five species of calanoid copepods from Long Island Sound contained DMSP, not associated with gut content, which varied interspecifically from 0.02 to 1.03 nmol ind. 1 . Carbon-specific DMSP content of the copepods was comparable to that reported for some diatoms, chlorophytes and cryptophytes. We argue that copepod biomass may, at times, represents a substantial source of particulate DMSP in the water column.

The disappearance of spawned copepod eggs can, at times, approach 100% day-' and may be a bottleneck to population recruitment of marine copepods. We examined the egg production rate and egg hatching success of Centropages hamatus and Temora longicomis (Copepoda: Calanoida) on natural diets, and the role of delayed hatching combined with high sinking rates in removing their eggs from the water column. Cumulative hatching success within IS days was consistently high from March to June 1996: -80% for Chamatus and 70% for T.longicornis. Minimum hatching time for C.hamatus was S days in winter and 1-4 days in spring. Minimum hatching time for T.longicornis was 3-3.5 days in winter and 1-2.S days in spring. We measured the diameter and density of eggs of both species to estimate sinking rates from Stokes' law. Sinking rates ranged from 4.6 to 22.4 m day1 for Chamatus and from 13.4 to 2S.4 m day~' for T.longicornis. In shallow waters like Long Island Sound (S20 m), in most cases virtually all the eggs may sink out of the water column before hatching starts. Therefore, we suggest that delayed hatching combined with a high sinking rate can be a significant cause for the high apparent egg mortality in copepods. We also discuss the consequences of egg sinking and asynchronous hatching in the estimation of in situ egg production.

Particles are responsible for the vertical transport of material in the ocean. Size is an important characteristic of a particle, determining its fall velocity, mass content, scattering crosssection, and food value, as well as other properties. The particle size spectrum describes the distribution of particles in a volume of water as a function of their sizes. We measured particle size spectra in Monterey Bay, CA, using six different instruments that examined particles ranging from approximately 1 μm to 10 mm. Before the results could be combined, they had to be adjusted for the different particle properties actually measured. Results from different optical instruments were similar, although the spectral values were sensitive to minor variations in the diameter assigned to particles. Sample volume was crucial in determining the effective upper size limit for the different techniques. We used fractal scaling to piece the results together, deriving fractal dimensions of 2.26–2.36. Diver observations of visible particles showed that they were composed mostly of aggregated diatoms. The particle size spectra n I were remarkably well fitted with a power law function n I = ad I − b I , where d I is the image diameter and b I = 2.96–3.00 . The equivalent slopes for particles measured with an aperture impedance instrument were 3.50–3.61. The particle volume distribution showed that most of the particle mass was in the 0.1–3 mm range. This volume distribution is consistent with theories that assume particle sizes are controlled by simultaneous coagulation and disaggregation.

Recent studies in the central equatorial Pacific allow a comprehensive assessment of phytoplankton regulation in a high-nutrient, low-chlorophyll (HNLC) ecosystem. Elemental iron enters the euphotic zone principally via upwelling and is present at concentrations (530 PM) well below the estimated half-saturation constant (120 PM) for the large cells that bloom with iron enrichment. In addition, the meridional trend in quantum yield of photosynthesis suggests that even the dominant small phytoplankton are held below their physiological potential by iron deficiency. Grazing by microzooplankton dominates phytoplankton losses, accounting for virtually all of the measured phytoplankton production during El Nina conditions and -66% during normal upwelling conditions, with mesozooplankton grazing and lateral advection closing the balance. Nitrate uptake is strongly correlated with the pigment biomass of diatoms, which increase in relative abundance during normal upwelling conditions. Nonetheless, the f-ratio remains low (0.07-0.12) under all conditions. Iron budgets are consistent with the notions that new production is determined by the rate of new iron input to the system while total production depends on efficient iron recycling by grazers. Although the limiting substrates differ, the interactions of resource limitation and grazing in HNLC regions are conceptually similar to the generally accepted view for oligotrophic subtropical regions. In both systems, small dominant phytoplankton grow at rapid, but usually less than physiologically maximal, rates; they are cropped to low stable abundances by microzooplankton; and their sustained high rates of growth depend on the remineralized by-products of grazing.

Using data collected during cruises of the JGOFS equatorial Pacific Study in March/April and October of 1992 at the equator (140°W), we examine the downward transport of carbon by three size classes of die] migrant mesozooplankton (200–500 gm, 500–1000 μm and 1000–2000 gm). In addition to respiratory carbon flux, we consider the flux due to mortality of migrators below the euphotic zone. Diel migrant mesozooplankton biomass was estimated from the difference between nighttime and daytime biomass within the euphotic zone. Except for a four-day period early in the March/April cruise, mesozooplankton nighttime biomass was significantly larger than daytime biomass within the euphotic zone during both cruises. We estimate that the downward flux of carbon from the euphotic zone due to mesozooplankton die] vertical migrators was an average of 0.6 mmol Cm −2 d −1 and 1.1 mmol C m −2 d −1 during the March/April and October cruises, respectively. Addition of this flux to the gravitational particle sinking flux estimated from 234 Th measurements during the same period results in a 31 % increase in the carbon export flux from the euphotic zone in the equatorial Pacific during the March/April cruise and a 44% increase in the October cruise. The migratory flux is strongly dependent on whether feeding takes place below the euphoric zone, the length of time migrators spend in the deep waters, and the mortality rate of migrators.

Many compelling management issues in Long Island Sound (LIS) focus on how organisms respond to stresses such as commercial and recreational harvesting, eutrophication, hypoxia, habitat degradation, invasion of non-native species, ocean acidification, and climate change. In order to address these complex problems, we must first understand the factors controlling biological processes and how organisms interact ecologically. This chapter provides an overview of the major groups of organisms occupying the dominant habitats of LIS.

The Glenlivet gas discovery made by DONG E&P and partners (Faroe Petroleum and First Oil) in 2009 is one of the most recent discoveries in the offshore West of Shetland region. The exploration target was an amplitude-supported stratigraphic prospect, and the discovery well 214/30a-2 proved the pre-drill model by finding gas-bearing Late Palaeocene sandstones of excellent quality in the Vaila Formation. The exploration success challenged the exploration history of the Faroe-Shetland Basin, where a number of amplitude-driven stratigraphic prospects led to exploration failures in the 1990s. The prospect was identified by means of high quality 3D seismic data and improved petrophysical and seismic understanding combined with regional mapping of the Vaila Formation sandstones. A detailed sedimentological and biostratigraphic understanding of the Palaeocene succession, in conjunction with the above, helped to de-risk the prospect and led to successful drilling.

Phytoplankton blooms are uncoupled from grazing and are normally terminated by sedimentation. There are several potential mechanisms by which phytoplankton cells may settle out of the photic zone: sinking of individual cells or chains, coagulation of cells into aggregates with high settling velocities, settling of cells attached to marine snow aggregates formed from discarded larvacean houses or pteropod feeding webs, and packaging of cells into rapidly falling zooplankton fecal pellets. We quantified the relative significance of these different mechanisms during a diatom bloom in a temperate fjord, and evaluated their potential to control phytoplankton population dynamics. Overall specific sedimentation rates of intact phytoplankton cells were low during the 11 -day study period, averaging ca. 0.1 d-l, and mass sedimentation and bloom termination did not occur. Most cells settled attached to marine snow aggregates formed from discarded larvacean houses, whereas settling of unaggregated cells was insignificant. Formation rates of phytoplankton aggregates by physical coagulation was very low, and losses by this mechanism were co.07 d-t; phytoplankton aggregates were neither recorded in the water column (by divers) nor in sediment traps. The low coagulation rates were due to a very low ‘stickiness’ of suspended particles. The dominant diatom, Thalassiosira mendiolana, that accounted for up to 75% of the phytoplankton biomass, was not sticky at all, and did not turn sticky upon nutrient depletion in culture experiments. The low particle stickiness recorded may be related to low formation rates by diatoms of transparent exopolymeric particles (TEP), that occurred in low concentrations throughout the study period. Zooplankton grazing rate did not respond to the development of the bloom and accounted for a loss term to the phytoplankton populations comparable to sinking of intact cells; fecal pellets accounted for 3&50% of settled phytoplankton and phytodetritus. While coagulation may give rise to density-dependent losses to phytoplankton populations and, hence, control blooms, neither of the other mechanisms 1. Danish Institute for Fisheries Research, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark (email: tk@dfu.min.dk) 2. Marine Biological Laboratory, Strandpromenaden 5, DK-3000 Helsinger, Denmark. 3. Marine Sciences Institute, University of California, Santa Barbara, California, 93106, U.S.A. 4. Department of Oceanography, Texas A&M University, College Station, Texas, 77843, U.S.A. 5. Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340-6097, U.S.A. 6. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02143, U.S.A. 7. Present address: School of Biological Sciences, Victoria University of Wellington, P.O. Box 600, Welling- ton, New Zealand. 8. Universidad de Cadiz, Department de Biologia Animal, Vegetal y Ecologia, Aptdo 40, E-l 1510 Puerto Real (Cadiz), Spain. 1123

We examined the relationship between egg production rate (£) and pigment ingestion rate (/, from gut content corrected for 33% loss) for adult female Temora longicornis in Long Island Sound on 47 occasions. Linear regression of E on / [both variables expressed in mass of nitrogen (N) female day] was: £N = 0.0016 + 0.770 x /N. The slope, 0.77, is the apparent gross efficiency of egg production, equivalent to the gross growth efficiency (GGE) assuming that females partition all nitrogen for growth into egg production. Published work suggests that a GGE of 0.37 would be expected for herbivorous copepods. The discrepancy between the expected value of 0.37 and observed value of 0.77 could result from unquantified losses of gut pigment or because T.longicomis ingested a significant amount of nitrogen by feeding as a carnivore. We suggest that if T.longicomis females derive all of their nitrogen for growth by feeding on phytoplankton, and if no correction for pigment loss is employed, then the gut pigment method underestimates pigment ingestion by no more than a factor of two. There is disagreement among zooplanktologists about whether measurements of gut pigments can be used to provide a quantitative measure of feeding rates. Some laboratory experiments have shown that measurements of gut pigment content (GPC) do not yield accurate estimates of ingestion rates because of high and variable amounts of pigment destruction—losses of 75-99% have been reported (Conover et al., 1986; Lopez et al., 1988; Penry and Frost, 1991; Cary et al., 1992). On the other hand, others have shown that pigment losses range from 0 to 30% (Dagg and Walser, 1987; Ki0rboe and Tiselius, 1987; Pasternak and Drits, 1988; Peterson etal., 1990; Penry and Frost, 1991). One reason for such a broad range in results is that laboratory experiments can be influenced by a copepod's feeding pre-history and by the degree to which an animal is acclimated to experimental conditions (Penry and Frost, 1991; Mayzaud and Razouls, 1992). An associated problem is that when one attempts to evaluate the GPC method by constructing a pigment budget, inaccuracies can arise because pigments can be lost easily during an experiment. The puzzle is that when one compares ingestion rates measured by GPC to ingestion rates estimated from another independent method (such as measuring ingestion rate from the disappearance of phytoplankton cells), the GPC method does not yield underestimates of ingestion rate (Ki0rboe et al, 1985a; Durbin et al, 1990; Peterson et al, 1990). Clearly, we have a problem here: does the gut pigment method produce accurate results or not? Can the gut pigment method be used for the purpose for which it was originally proposed (Nemoto, 1968; Mackas and Bohrer, 1976), i.e. to estimate ingestion rates of zooplankton feeding on phytoplankton? In this paper, we evalu© Oxford University Press 855 W.T.Peterson and H.G.Dam ated the GPC technique by comparing ingestion estimated from GPC to ingestion estimated by measuring egg production rates of adult female copepods in Long Island Sound. Egg production is related to ingestion through gross growth efficiency (GGE) by

The 1995 summer season saw continued petroleum activities in West Greenland, both onshore and offshore. The activities took place both as major geological and geophysical projects led by the Geological Survey of Denmark and Greenland (GEUS)