Maciej Wołowicz

Geographic and seasonal patterns and limits on the adaptive response to temperature of European Mytilus spp. and Macoma balthica populations

Seasonal variations in seawater temperature require extensive metabolic acclimatization in cold-blooded organisms inhabiting the coastal waters of Europe. Given the energetic costs of acclimatization, differences in adaptive capacity to climatic conditions are to be expected among distinct populations of species that are distributed over a wide geographic range. We studied seasonal variations in the metabolic adjustments of two very common bivalve taxa at European scale. To this end we sampled 16 populations of Mytilus spp. and 10 Macoma balthica populations distributed from 39° to 69°N. The results from this large-scale comprehensive comparison demonstrated seasonal cycles in metabolic rates which were maximized during winter and springtime, and often reduced in the summer and autumn. Studying the sensitivity of metabolic rates to thermal variations, we found that a broad range of Q10 values occurred under relatively cold conditions. As habitat temperatures increased the range of Q10 narrowed, reaching a bottleneck in southern marginal populations during summer. For Mytilus spp., genetic-group-specific clines and limits on Q10 values were observed at temperatures corresponding to the maximum climatic conditions these geographic populations presently experience. Such specific limitations indicate differential thermal adaptation among these divergent groups. They may explain currently observed migrations in mussel distributions and invasions. Our results provide a practical framework for the thermal ecophysiology of bivalves, the assessment of environmental changes due to climate change and its impact on (and consequences for) aquaculture.

Comparative analysis of oxygen consumption rates between cupped oyster spat of Crassostrea gigas of French, Japanese, Spanish and Taiwanese origins

Respiration rates of various geographical strains of Crassostrea gigas were compared to assess the respiratory expenditure as a physiological indicator of catabolism (cost of maintenance). Parental oysters, sampled in France (Marennes-Oleron), Japan (Hiroshima), Taiwan (Tunkang) and Spain (Cadix), were differentiated by both their geographic origin and by mitochondrial DNA markers, allowing the distinction between the two cIosely related taxa Crassostrea gigas and Crassostrea angulata. After reproduction of these parental oysters, respiration rates of spat of each strain, reared under common controlled conditions, were individually estimated at 20 oC by using a volumetric microrespirometer. Our results demonstrated that physiological variability existed among the Crassostrea gigas strains and is likely to be related to physiological differences between geographical regions and/or genetic adaptations. The French strain showed the highest rates (0.71 IlL·h-I), while the Japanese, Taiwanese and the hybrid between Spanish and French strains consumed less, 0.53, 0.43 and 0.40 IlL·h-l, respectively. Our results confirmed the discrepancies previously suggested between Crassostrea gigas and Crassostrea angulata. Comprehensive physiological assessments should be carried out over a wide temperature range to confirm our results and to further evaluate growth potential. Appropriate decision making based on these studies will help future shellfish management in shellfish rearing areas such as the overstocked Marennes-Oleron Bay.

Distribution of dissolved and labile particulate trace metals in the overlying bottom water in the Vistula River Plume (Southern Baltic Sea)

Overlying bottom water samples were collected in the Vistula River plume, southern Baltic Sea, (Poland) and analysed for dissolved and labile particulate (1 M HCl extractable) Cu, Pb, Zn, Mn, Fe and Ni, hydrological parameters being measured simultaneously. Particulate organic matter (POM), chlorophyll a and dissolved oxygen are key factors governing the chemical behaviour of the measured metal fractions. For the dissolved Cu, Pb, Zn, Fe and Ni two maxima, in the shallow and in the deeper part of the river plume, were found. In the shallow zone desorption from seaward fluxing metal-rich riverine particles account for markedly increased metal concentrations, as confirmed also by high particulate metal contents. For Pb, atmospheric inputs were also considered to have contributed to the elevated concentrations of dissolved Pb adjacent to the river mouth. In the deep zone desorption from detrital and/or resuspended particles by aerobic decomposition of organic material may be the main mechanism responsible for enrichment of particle-reactive metals (Cu, Pb, Zn) in the overyling bottom waters. The increased concentrations of dissolved Fe may have been due to reductive dissolution of Fe oxyhydroxides within the deep sediments by which dissolved Ni was released to the water. The distribution of Mn was related to dissolved oxygen concentrations, indicating that Mn is released to the water column under oxygen reduced conditions. However, Mn transfer to the dissolved phase from anoxic sediments in deeper part of the Vistula plume was hardly evidenced suggesting that benthic flux of Mn occurs under more severe reductive regime than is consistent with mobilization of Fe. Behaviour of Mn in a shallower part has been presumably affected by release from porewaters and by oxidization into less soluble species resulting in seasonal removal of this metal (e.g. in April) from the dissolved phase. The particulate fractions represented from about 6% (Ni) and 33% (Mn, Zn, Cu) to 80% (Fe) and 89% (Pb) of the total (labile particulate plus dissolved) concentrations. The affinity of the metals for particulate matter decreased in the following order: Pb > Fe > Zn > or = > Cu > Mn > Ni. Significant relationships between particulate Pb-Zn-Cu reflected the affinity of these metals for organic matter, and the significant relationship between Ni-Fe reflected the adsorption of Ni onto Fe-Mn oxyhydroxides. A comparison of metal concentrations with data from other similar areas revealed that the river plume is somewhat contaminated with Cu, Pb and Zn which is in agreement with previous findings on anthropogenic origin of these metals in the Polish zone of southern Baltic Sea.

Chromosomal study of spatial variation of the prevalence of a gill neoplasia in Macoma balthica (L.) from the Gulf of Gdansk (Baltic Sea)

Abstract Spatial variation of the prevalence of a gill neoplasia in the bivalve Macoma balthica was investigated by chromosomal study of individuals from ten different sites in the Gulf of Gdansk. The prevalence of gill neoplasia, individually identified by the occurrence of abnormal metaphases with higher chromosome numbers than normal metaphases (2n = 38), ranges from 0 to 94% of individuals, according to the site studied. Sites Hel 45 m and Vistula 30 m, located in the zone of the thermocline and halocline were the most affected, probably related to very unstable hydrological conditions at these sites. Out of a total of 152 animals studied from the Gulf of Gdansk, 33% showed the occurrence of gill neoplasia. A chromosome number from 59 to 109 was scored in 29 abnormal metaphases. Karyotypes were constructed from 14 abnormal metaphases and showed a similar general pattern. This study showed that chromosomal abnormalities involving numerical and morphological changes imply similar disorders among the sites studied. Etiology of this disease is still unknown but the seriously polluted Gulf of Gdansk can be used as a model basin to assess the relationship between the incidence of neoplasia and the possible controlling factors of environmental instability and/or level of environmental contaminants.

Physiological responses of Macoma balthica to copper pollution in the Baltic

Physiological and behavioral responses to Cu exposure were measured in the Baltic clam Macoma balthica from the Gulf of Gdansk, southern Baltic Sea. The burrowing activity, mortality rate, glycogen content, condition index and free amino acid (FAA) composition were analysed as indicators of stress in a series of field and laboratory studies. M. balthica exposed to Cu showed clear Cu-concentration related differences in burrowing activity and mortality rate, but no consistent differences in the condition index, glycogen content, and free amino acids. The clams from a less polluted area reacted more strongly and were more sensitive to additional stress as compared to organisms from a more polluted region. The effect of Cu on the ecophysiology of Baltic clams in the field was probably obscured by reproduction-related changes in the organism. The role of sediment as a potential source of Cu in the Baltic clam was discussed.

Ecophysiological and Genetic Traits of the Baltic Clam Macoma balthica in the Baltic: Differences between Populations in the Gdansk Bay Due to Acclimatization or Genetic Adaptation?

Normal and irregular blunt clam-shells were found. Blunt shells increased with depth, because of increasing anoxia. Minimal weight-indices and reproductive stages were found at 40 m depth (near thermo-haline stratification) probably due to spawning just before sampling. Clams from shallower stations were more ripe and heavier due to higher temperatures and re-development than at deeper stations since temperatures were still below threshold levels for spawning (10 °C). Respiration was at ambient temperatures acclimated to standard rates. Consequently, clams from deeper stations (with lower ambient temperatures) had 2 times higher respiration at the same test-temperature. Clams from the most shallow station (Puck Lagoon 5 m) showed the worst performance due to adverse hydrodynamics (stagnated water, anoxia). Heterozygotes showed better performance than homozygotes (heterosis). In 1995 genetic differentiation was found (Idh was diagnostic): clams below 30 m resembled Atlantic populations; shallow stations formed a distinct group (Baltic race). In later years all populations were Atlantic, probably due to inflow of North Sea water. Before 1996 ecophysiological differences between clams in the Gdansk Bay can possibly be related to genetic differentiation (adaptations of Atlantic vs. Baltic types), in later years differences were due to acclimation to ambient temperatures, salinity and oxygen levels.

Free amino acids in the clam Macoma balthica L. (Bivalvia, Mollusca) from brackish waters of the southern Baltic Sea

Fourteen acidic and neutral free amino acids (FAA) were investigated in soft tissue of Macoma balthica from different depth zones of the Gulf of Gdansk (Baltic Sea) over a full seasonal cycle. The dry weight of the bivalves and physico-chemical parameters of overlying bottom water and surface sediments were measured simultaneously at each site. In the brackish waters of the Baltic, the main pool of FAA is composed of Ala, Gln, Arg, Gly and Orn which represent approximately 80% of the total. Compared to the full saline environments, the composition of FAA in the clams from the Baltic differs substantially. The differences can be attributed to the lower salinity of the Baltic. In the Baltic, Gly appears to play a most important role in regulating intracellular osmolarity in the clams, a function performed primarily by Tau in Atlantic and North Sea populations. Spatio-temporal variations of the FAA are affected by biotic and environmental parameters; their respective influence differs with the amino acids. The concentration of Arg depends on its uptake from the external medium. However, its level might be temporarily modified by stress-induced metabolic transformation (e.g. hydrolysis to Orn) caused by changes in the ambient environment. The concentration of Ala increases with depth, probably because of physiological adaptations of the animal to diminishing oxygen concentration through anaerobic glucose catabolism. Biosynthesis of Ala, similarly to Gln, in the shallower zone is generally related to the physiological state of an organism. The concentration of Gly is most likely regulated by internal mechanisms driven by gonadal development and reproduction.

Comparison of trace metal bioavailabilities in European coastal waters using mussels from Mytilus edulis complex as biomonitors

Mussels from Mytilus edulis complex were used as biomonitors of the trace metals Fe, Mn, Pb, Zn, and Cu at 17 sampling sites to assess the relative bioavailability of metals in coastal waters around the European continent. Because accumulated metal concentrations in a given area can differ temporally, data were corrected for the effect of season before large-scale spatial comparisons were made. The highest concentration of Fe was noted in the North Sea and of Mn in the Baltic. Increased tissue concentrations of Pb were recorded in the mussels from the Bay of Biscay and the Baltic Sea. Low concentrations of metals were determined in the mussels from the Mediterranean Sea and the Northern Baltic. Relatively low geographic variations of Cu and Zn indicate that mussels are able to partially regulate accumulated body concentrations, which means Cu and Zn are, to some extent, independent of environmental concentrations.

Shell deformations in the Baltic clam Macoma balthica from southern Baltic Sea (the Gulf of Gdansk): hypotheses on environmental effects.

Abstract High-resolution digital photography and graphical image analyses systems have been used to define external morphometric characters of shell deformations in four populations of the Baltic clam Macoma balthica from the Gulf of Gdansk (southern Baltic Sea). The proposed shell deformation indices (SDI), which were based on the relationship of selected dimensions in the posterior and the anterior part of the shell, showed at least three morphological features that provide a distinctive diagnosis of “regular” and “deformed” clams: the presence of flexure on the posterior side (SDI1), elongated posterior region (SDI2), and shell growth (SDI3). The degree and prevalence of deformed clams varied locally over space. Increase in percentage contribution of aberrated shells with depth, corresponding to oxygen depletion profile in the Gulf, suggests low oxygen concentrations as the main agent exerting a deforming influence. The observed morphological aberrations developed with age (size) of a bivalve, suggesting a long-term effect of causal factors, and were accompanied by lightening shell weight, possibly due to decalcification of previously deposited calcareous material during anaerobic metabolism. It is hypothesized that hypoxic/anoxic conditions and a subsequent presence of hydrogen sulfide on a deep organic-rich sea bottom induce shell form alterations that enable the pumping of oxygenated water from above the anoxic layer. Such a morphological modification highlights the functional significance of shell deformations in protective response to the ambient low-oxygen concentrations. Sediment organotin concentrations fall within moderate to high contamination range and, therefore, may also have an adverse impact on the shell form. DNA analyses of the fragment of mitochondrial gene cytochrome oxidase I (COI, 393 base pairs) showed homogenous genetic structure of regular and deformed clams, indicating that shell deformations in M. balthica are primarily driven by acclimatization to the ambient environmental conditions.

Differences in reproduction and condition of Macoma balthica and Mytilus trossulus in the Gulf of Gdańsk (Southern Baltic Sea) under anthropogenic influences.

Differences in reproduction and condition of Macoma balthica and Mytilus trossulus in the Gulf of Gdańsk (Southern Baltic Sea) under anthropogenic influences Seasonal changes in gametogenesis, spawning behaviour and morphometric parameters of Macoma balthica and Mytilus trossulus from two depth zones in the Gulf of Gdańsk (Southern Baltic Sea) were investigated. The studies allowed the authors to make observations of the ecophysiological features of both species and revealed major differences in the weight index between deep and shallow water subpopulations. Both condition and gametogenesis probably depend mainly on the availability of nutrients and on temperature changes. The data showed that Mytilus trossulus spawned earlier at the shallow water station than at the deeper one. No differences were observed between the run of the Baltic clams reproductive cycle at 10 m and at 75 m depths.