Amphipod Monoporeia Affinis Research Articles

Biomarker sensitivity to temperature and hypoxia — a seven year field study

We examined the response of a set of reproduction biomarkers to natural climate vari- ables such as oxygen concentration, temperature and organic carbon (OC) in sediment. The data used was from field studies of the amphipod Monoporeia affinis covering 7 consecutive years from 1994 to 2000. Our aims were to evaluate the sensitivity of the biomarker 'malformed embryos' to oxy- gen deficiency, temperature increase and OC in sediments and to perform a field validation of some reproduction biomarkers targeted at these factors. The biomarker 'malformed embryos' was related neither to oxygen concentration nor to temperature, while a relationship was found with OC content of the sediment. A negative correlation was found between females carrying a dead brood and the oxygen concentration of the bottom water. Fecundity was positively correlated with the carbon con- tent of the sediment but negatively correlated with the temperature of the bottom water. These results confirm the findings of previous laboratory experiments. By combining a set of biomarkers of different sensitivity to various stressors, we have obtained a powerful tool capable of monitoring the effects of both contaminants and other environmental stressors, and with the ability to discriminate between the effects of different environmental disturbances.

Dynamics of lipids and polychlorinated biphenyls in a Baltic amphipod (Monoporeia affinis): a field study.

Processes such as accumulation and elimination, which control tissue concentration of polychlorinated biphenyls (PCBs), were examined over time in an in situ study of the amphipod Monoporeia affinis. These processes were studied with respect to individual PCB congeners, percentage lipid and composition, and body weight. A secondary objective was to examine the impact of seasonal variability in percentage lipids and lipid composition on PCB concentration in two coexisting Baltic amphipods, M. affinis and Pontoporeia femorata. Polycholorinated biphenyl concentrations tended to be higher in P. femorata than in M. affinis, possibly because of P. femorata's lower respiration rate and larger size. The net accumulation of PCBs was congener dependent and negatively correlated to lipid concentration. The relation between the net concentration change rate of 16 PCB congeners over time and log Kow was not significant during the spring and summer months, a time when lipid accumulation and strong growth occur. In contrast, the net concentration change rate of the corresponding PCB congeners over time during autumn and early winter, that is, from the period before gonad maturation to the period after mating and early embryogenesis, showed a significant relation to tog Kow (r2 = 0.62, p < 0.001, n = 16). During the latter period, amphipod lipid weight was reduced while the PCB body burden increased. Results strongly indicate that elimination rather than accumulation is the main process controlling amphipod body burden. This pattern results in a transfer of PCBs from the female to the developing embryos, which is reflected in high PCB body burden in newly released offspring.

Competition for food between the introduced polychaete Marenzelleria viridis (Verrill) and the native amphipod Monoporeia affinis Lindström in the Baltic Sea

Since 1985 the spionid polychaete Marenzelleria viridis (Verrill) has invaded large parts of the Baltic Sea. In deeper soft-bottom habitats (>10 m) a marked long-term decrease of the native amphipod Monoporeia affinis has been noted and is presently associated with the establishment of the polychaete. One plausible explanation is that the polychaetes and the amphipods are competing for food resources as both are deposit feeding animals and likely to share similar food resources. Interspecific competition for food between the polychaete and the amphipod was studied in a laboratory experiment. Two year classes (0y+,1y+) of the amphipods were kept at various densities, with and without added food resources, with and without the polychaete, in microcosms with sediment and continuous supply of cooled water for 2 months. The polychaetes did not have any effect on mortality in the amphipods. 4-way ANOVA showed that food addition, density of amphipods and presence of the polychaete had a significant effect on the growth of amphipods of different age classes. 1y+ amphipods showed increased growth with added food and this increase was density-dependent in the absence of the polychaetes but not in their presence. The polychaetes reduced the growth of 1y+ amphipods at natural densities (2000 ind m −2) by 60%, but had no clear effects on the growth of juveniles. It is concluded that lower amphipod growth in the presence of M. viridis was caused by competition for food and is likely to affect the population of M. affinis in deep soft-bottom habitats of the northern Baltic Sea.

Effects of biological disturbance by Monoporeia affinis (Amphipoda) on small-scale migration of marine nematodes in low-energy soft sediments

Free-living marine, benthic nematodes quickly colonise sediments where physical forces are strong enough to suspend them into the water column. In the absence of such forces colonisation is much slower and is more likely to be affected by biological factors. The aim of the study was to investigate if nematodes disperse more readily in the presence of biological disturbance where physical disturbance is rare or non-existent. Amphipods are able to greatly rework sediments, and thereby induce disturbance to the infauna. A laboratory experiment with the amphipod Monoporeia affinis and nematodes from a low-energy, 30-m-deep location was conducted in mesocosms where the nematodes were given the choice to colonise azoic sediment at three amphipod densities, zero, low and high. Each area of azoic sediment in the mesocosms was divided into three equilateral sections from the nematode source, i.e. 10, 23 and 36 cm. At termination, after 7 weeks, there were no significant differences in nematode abundance and assemblage structure between treatments despite considerable biological disturbance created by the amphipods. The number of nematodes was 16%, 15% and 11% of the total numbers in the source at the three sections 10, 23 and 36 cm, respectively. There were distinct differences in the nematode community composition between distances, with the small surface-dwelling taxon Leptolaimus spp. being a rapid and the numerically dominant coloniser of the azoic sediments. Migration of nematodes over short distances is likely to be slow in the absence of strong physical forces. To our knowledge, this is the first paper ever that investigates the influence of macrofauna on nematode short-range migration.

Competition between the introduced polychaete Marenzelleria sp. and the native amphipod Monoporeia affinis in Baltic soft bottoms

The North American spionid polychaete Marenzelleria cf. viridis was reported from the Baltic Sea for the first time in 1985. The species has spread rapidly and now dominates many soft- bottom communities, where it dwells in burrows down to 30 cm deep in the sediment. In the Baltic Sea, below 10 m water depth, the macrobenthic community is composed of only a handful of species, among which the amphipod Monoporeia affinis is a key member. This species is highly mobile; it swims actively at night but remains burrowed in the sediment during the day. Due to similarities in feeding mode and sympatric occurrence, the polychaete may compete with the amphipod for both food and space. One plausible outcome of interactions between the 2 species is that the amphipod, the more mobile species, would avoid areas where the more sessile polychaete is present in high numbers. In the laboratory, we tested the hypothesis that, if given the choice, the amphipod avoids burrowing in sediment with high polychaete abundances. The amphipod burrowed in significantly lower numbers in patches with high polychaete abundance compared to those with lower abun- dance. Also, plastic tubes mimicking polychaete body structure were not avoided by the amphipods, indicating that the physical tube structure of the polychaetes does not explain the amphipod's choice of burrowing site. Furthermore, the amphipod did not increase or prolong swimming activities as a function of higher worm density, indicating that increased swimming activity over dense polychaete patches and subsequent migration away from them is not a likely explaination of why this amphipod burrow less frequently in patches of high polychaete abundance.

Bioavailability of metals to the amphipodMonoporeia affinis: Interactions with authigenic sulfides in urban brackish‐water and freshwater sediments

Could reduced eutrophication be a potential environmental threat because of increased mobility and bioavailability of trace metals? This question was addressed by oxygenating intact sediment cores, varying in redox potential and salinity, in a test system containing the amphipod Monoporeia affinis. Results show a low mobility of metals during oxygenation, and despite high concentrations of metals in sediments, only Pb showed a notable degree of bioaccumulation. Cadmium was bioaccumulated particularly in freshwater sediment, and body burden of Cd was related to salinity, porewater, and sediment concentrations. Despite high sediment and porewater concentrations of Cu and Zn, no relationship was recorded to body burden. For three of four tested metals, Cd, Pb, and Zn, metals in sediment were more important for body burdens in amphipods as compared to metals in porewater. Food, rather than interstitial water, therefore seems to be the main route of metal contaminants to these amphipods. Furthermore, this observed low release of metals from sediments and low body burden significance of porewater metals indicate that ameliorated oxygen conditions in contaminated sediments may be regarded as a minor environmental threat for one of the most important Baltic benthic organisms.

Estimating predation rates in experimental systems: scale‐dependent effects of aggregative behaviour

We studied the effect of arena size on estimates of prey mortality rate in predation experiments. In a laboratory experiment involving two of the dominating benthic species in the northern Baltic Sea, the predacious isopodSaduria entomon, and its main prey, the amphipodMonoporeia affinis, the prey mortality rate increased with container radius. The densities of both predator and prey close to the wall increased with container size. We hypothesised that this scale‐dependent coaggregation of predator and prey caused the mortality rates to increase with arena size. We tested the hypothesis with the help of a simple model, by calculating the expected number of prey eaten in containers of different size from experimental data on the distributions of predator and prey within the arenas. A significant relationship between expected and observed numbers eaten supported our hypothesis. As the aggregative response was most pronounced in large arenas, this leads to the counterintuitive conclusion that large containers produced more biased estimates of morality rates than small containers. To further study the effects of coaggregation we explored a general simulation model where both predator and prey preferred the habitat close to the arena wall. The model predicted a humpshaped relationship between encounter rate and arena size. This suggests that when predators and prey show a scale‐dependent tendency to aggregate along arena walls, the most accurate estimates of predation rates may be obtained with very small or very large arenas.

Intraspecific competition for food within and between year classes in the deposit-feeding amphipod Monoporeia affinis-the cause of population fluctuations?

We investigated whether intraspecific competition for food and/or other possible density- dependent interactions occurred within and between 2 age classes of the deposit-feeding amphipod Monoporeia affinis. A 2-factor laboratory experiment was conducted, where juveniles (0+) and adults (1+) were kept in experimental jars for 2 mo at densities of 2000, 4000 and 8000 ind. m -2 , which cor- responds to natural abundances in the Baltic Sea. The amphipods were fed on a mixture of naturally occurring algae at 3 food levels: zero, medium (representing a diatom spring-bloom) and high (rep- resenting a 2 × diatom spring-bloom). The level of food added to the experimental jars determined whether food competition occurred, both within and between the 2 age classes. Growth of juveniles was not density-dependent, at any food level, in the absence of adults, but clearly dependent on pres- ence or absence of fresh algal material. In presence of high adult densities, the growth of juveniles was significantly reduced at food levels that corresponded to a single and twice a diatom spring- bloom, while such reduction was not found in jars without added algae. Growth of adults was both density- and food-dependent. Juveniles did not affect the survival and growth of adults. As high den- sities of amphipods in jars without added food affected neither growth nor mortality, we conclude that crowding effects such as predation or directly damaging interference are not important regulat- ing mechanisms. The results indicate that exploitative intraspecific competition for food occurs both between and within year classes, but depends on the resource levels and is likely to be most intense under a regime of low to medium input of phytodetritus. The experiment lends support to the hypoth- esis that intraspecific competition for food acts as an important process causing fluctuations in the Baltic Sea populations of M. affinis.

Factors affecting population fluctuations of the glacial relict amphipod Monoporeia affinis (Lindström) in Sweden's largest lakes.

Factors affecting long-term (1982-2000) population densities of the glacial relict amphipod Monoporeia affinis were studied in Sweden's three largest lakes. Monoporeia showed large population fluctuations in all three lakes, with conspicuous peaks in density occurring in Lakes Vänern and Mälaren. In Lake Vänern, amphipod densities showed highly significant relationships with spring maximum diatom biovolume at a 1-yr lag. The lack of relationship between diatom biovolumes and Monoporeia densities in L. Vättern is likely due to the larger depth and the lower nutrient content of this lake. In eutrophic L. Mälaren, summer hypoxia (< 4 mg O2 L-1) is likely an important regulating factor. Hypolimnetic temperature showed a clear periodicity with relatively warm deep water occurring between 1989 and 1994. Hypolimnetic temperatures in Vänern and Vättern were correlated with total solar irradiance. However, neither hypolimnetic water temperature nor diatom biovolumes correlated with the North Atlantic Oscillation winter index. We speculate that variations in temperature and near-bottom oxygen concentrations negatively affect population densities by acting on recruitment success (reproduction) and juvenile (young-of-the-year) survival.

Predation by the benthic isopod Saduria entomon on two Baltic Sea deposit-feeders, the amphipod Monoporeia affinis and the bivalve Macoma balthica

This laboratory study demonstrates that Saduria entomon prefers the amphipod Monoporeia affinis over the bivalve Macoma balthica. When offered bivalves only, S. entomon selects the smaller individuals. Predation by S. entomon may thus alter the species composition and size distributions of its prey community, which in the field is often dominated by these two species. When offered one M. balthica size class at a time, 30-mm-long isopods ate only bivalves of the 2–3 and 6–7 mm size classes and rejected classes 10–11 and 15–16 mm, even though they can open them. More bivalves were eaten in the 2–3 mm size class than in the 6–7 mm class, but energy yield was slightly higher from the 6–7 mm class. When 10- to 45-mm-long S. entomon were offered a range (1–22 mm) of bivalve sizes, they consistently selected small prey. The length of the largest bivalve eaten increased with predator size, without the smallest bivalves being excluded from the diet. Energy consumed increased with increasing predator size. The size-selective predation in our experiment results in preferential survival of larger prey. When given a choice between ∼5-mm-long M. balthica and ∼7-mm-long M. affinis in ratios of 0:40, 10:30, 20:20, 30:10 and 40:0 (total density of 3600 m −2), S. entomon clearly preferred the amphipod (preference constant 69), and ate very few bivalves. In the treatment with 30 bivalves and 10 amphipods, bivalves were not as strongly selected against as in other two-prey treatments. In a 28-day prey depletion experiment with an initial 1:1 prey ratio, almost all amphipods were consumed in the first week, after which bivalves started to be eaten.

Deposit-feeding amphipods ( Monoporeia affinis ) reduce the recruitment of copepod nauplii from benthic resting eggs in the northern Baltic Sea

We experimentally investigated the effect of different densities of the burrowing, deposit-feeding amphipod Monoporeia affinis on the recruitment of zooplankton from benthic resting eggs. Intact se ...

Survival and bioturbation of the amphipod Monoporeia affinis in sulphide-rich sediments

Laboratory experiments were conducted to investigate the survival rate of Monoporeia affinis in sulphide-rich sediment with oxic overlying water, and the effect of amphipod bioturbation on sulphide and oxygen profiles. As long as the oxygen content in the water is high, the amphipods seem to avoid quite high concentrations (>200 μmol l−1) of sulphide in the sediment by creating microhabitats where sulphide is rapidly oxidised. In cores with amphipods, a decrease of sulphide concentration was found in upper layers, while an increase of sulphide was found in deeper layers. Aggregation of amphipods generated pockets of light-brown sediment, characterised by high oxygen concentrations and no sulphide, and their depth was clearly dependent on amphipod density. This indicates that M. affinis has a potential to recolonise sulphide-rich sediments, devoid of macroscopic life, after the overlying water column has become oxygenated.

Impaired reproduction in the amphipods Monoporeia affinis and Pontoporeia femorata as a result of moderate hypoxia and increased temperature

Laboratory experiments were performed on the amphipods Monoporeia affinis and Pon- toporeia femorata in order to test the hypotheses that specific reproductive variables are affected by moderate hypoxia and/or slightly increased temperature. These reproductive variables include unfertilised/undeveloped eggs, dead eggs and females carrying a dead brood. In a series of experi- ments, amphipods were exposed to increased temperature during different parts of the reproduction cycle. Exposure prior to mating caused an increased number of dead eggs and a higher percentage of females carrying dead broods. Furthermore, the effects of low oxygen concentrations (2 to 6 mg O2 l -1 ), solely and in combination with contaminated sediments, heavy metals and hydrophobic organic con- taminants (polycyclic aromatic hydrocarbons and polychlorinated biphenyls), were tested during the reproduction cycle. Exposure to low oxygen concentrations induced a higher frequency of females carrying dead broods, and females exposed to hypoxia or contaminants had a lower fertility rate com- pared to controls. Our results show that oxygen concentrations and temperature conditions normally occurring in the Baltic Sea and that are not otherwise detrimental to adults could severely affect the gonads and the embryos. Females with dead broods, undeveloped/unfertilised eggs and dead eggs are proposed as tools for use in monitoring non-contaminant stressors.

Intraspecific food competition in the deposit-feeding benthic amphipod Monoporeia affinis-a laboratory study

Field studies in the Baltic Sea indicate that the growth rate of the deposit-feeding ben- thic amphipod Monoporeia affinis (Lindstrom), which is found in densities of up to ≅25 000 ind. m -2 , is negatively density-dependent. We tested the density-dependence of growth in M. affinis under controlled laboratory conditions, using sediment of high organic content (loss on ignition 10.9%) and a wide density range of 2 amphipod year-classes (juveniles, 1150 to 38 000 ind. m -2 , 1 yr old sub- adults, 580 to 18 000 ind. m -2 ). Growth was strongly negatively density-dependent for both juveniles and subadults. We then used sediment of low organic content (loss on ignition 3.7%) to test whether the density-dependence of growth was due to a direct crowding effect at high density, or mainly due to food limitation. Using an intermediate amphipod density (2800 ind. m -2 ) expected to give clear growth depression, we added baker's yeast as supplementary food at 6 levels corresponding to an input of 0 (control) to 147 g C m -2 over an 8 wk period. The 3 highest yeast additions resulted in black, reduced sediment and elevated amphipod mortality in some replicates, but where the sediment did not become reduced, food additions enhanced growth significantly, demonstrating that growth depression at high density was primarily due to food limitation and not to crowding as such.

Factors Affecting Population Fluctuations of the Glacial Relict Amphipod Monoporeia affinis (Lindström) in Sweden's Largest Lakes

Factors Affecting Population Fluctuations of the Glacial Relict Amphipod Monoporeia affinis (Lindström) in Sweden's Largest Lakes

Toxic Substances and Reproductive Disorders in Baltic Fish and Crustaceans

In the Baltic Sea ecosystem reproductive disorders have occurred in top consumers such as seals and some fish-eating birds, due to biomagnification of toxic substances, e.g. DDT and PCBs. Reproductive disturbances have also affected fish during the last 25 years. However, there is no strong evidence that toxic substances have caused these problems. Rather, the disorders seem to result from a combination of two or more biotic or abiotic factors. The M74 syndrome, which kills fry of salmon and sea trout, is characterized by a deficiency of thiamine (vitamin B1). Several factors may contribute to the thiamine deficiency, including the diet of salmon in the sea and halogenated organic compounds. Cod do not develop M74, and poor cod recruitment is mainly due to poor oxygen conditions in the spawning areas in combination with overfishing. Toxic compounds in pulp-mill effluents retard gonadal development in perch, but the mechanisms and the active substances have not been identified. Recruitment problems in perch in the coastal waters outside some pulp mills may also be explained by a lack of food items for juvenile fish, rather than reproductive failure. There are very limited data on reproductive disorders in crustaceans from the Baltic Sea. Most data come from studies of the benthic amphipod Monoporeia affinis, which has been used in monitoring programs. Several signs of reproductive disorder have been reported in this amphipod, e.g. malformation and death of embryos, and asynchronous maturation of males and females.

Swimming behaviour in Monoporeia affinis (Crustacea: Amphipoda) - dependence on temperature and population density.

Swimming speed and swimming activity of the nocturnally active benthic amphipod Monoporeia affinis were measured in water temperatures from 3 to 18 degrees C and different population densities in the laboratory. Swimming speed increased with increasing temperature. Increasing water temperature reduced the percentage of active animals in the population, as measured by a "freeze frame" technique. At 7 and 10 degrees C a higher percentage of the population was active in higher animal densities. In all tested conditions swimming activity was highest at about 1 h after light-off and lowest shortly before the predicted time of light-on. The consequences of the documented behavioural responses to environmental stimuli are discussed in relation to population dynamics.

Benthic predator-prey interactions: evidence that adult Monoporeia affinis (Amphipoda) eat postlarval Macoma balthica (Bivalvia).

Predation by adults of the amphipod Monoporeia affinis on the plantigrade postlarval stage of the bivalve Macoma balthica was studied in the laboratory. We confirmed that M. affinis consumes small M. balthica. Amphipods offered 14C-labelled postlarvae took up the radioactive tracer, while those presented Rhodamine B-stained postlarvae acquired gut contents fluorescing strongly in orange, whereas control amphipods did not. Both labelling methods proved convenient to use in laboratory experiments, and are particularly useful when organisms lack structures that can be easily identified after being ingested, or when cross-over reactions may bias the results of immunoassays. The results reported here support the conclusion from earlier studies that predation by M. affinis on M. balthica can affect population dynamics of M. balthica and is likely to be an important structuring factor in the low-diversity benthic macrofauna community of the Baltic Sea.

Breakdown of phytoplankton pigments in Baltic sediments: effects of anoxia and loss of deposit-feeding macrofauna.

We examined the decay of chlorophyll a and the carotenoid fucoxanthin in oxic and anoxic sediment microcosms, with and without the deposit-feeding benthic amphipod Monoporeia affinis, over 57 days at 5 degrees C. Deep frozen phytoplankton from the Baltic Sea proper was added to all but a few microcosms. The range of chlorophyll a and fucoxanthin decay rate constants observed in microcosms with phytoplankton addition was 0.04-0.07 day(-1). The fastest pigment decay and build-up of chlorophyll breakdown products after phytoplankton addition were found in oxic treatments with amphipods. No effects of amphipods on pigment breakdown were found in anoxic treatments, or in treatments without phytoplankton addition. Greater losses of chlorophyll a in oxic (96%) than in anoxic (80%) treatments after 57 days indicates that preservation of sedimentary organic matter will be enhanced during periods of anoxia. Due to slow recruitment and recolonization in Baltic sediments, a single anoxic event may cause long-term (years) absence of significant macrobenthos. Anoxic events will thus not only reduce decay of plant pigments, and presumably other organic matter, while they last, but will also have longer-term effects, through elimination of macrofauna, which when present enhance organic matter decomposition.

Impact of a burrowing deposit-feeder, Monoporeia affinis , on viable zooplankton resting eggs in the northern Baltic Sea

We investigated the effect of different densities of the burrowing deposit-feeding amphipod Monoporeia affinis on the potential for recruitment of zooplankton from benthic resting eggs. Hatching of ...