Tina Elfwing

Evidence of population genetic effects of long-term exposure to contaminated sediments-a multi-endpoint study with copepods.

In the environment, pollution generally acts over long time scales and exerts exposure of multiple toxicants on the organisms living there. Recent findings show that pollution can alter the genetics of populations. However, few of these studies have focused on long-term exposure of mixtures of substances. The relatively short generation time (ca. 4-5 weeks in sediments) of the harpacticoid copepod Attheyella crassa makes it suitable for multigenerational exposure studies. Here, A. crassa copepods were exposed for 60 and 120 days to naturally contaminated sediments (i.e., Svindersviken and Trosa; each in a concentration series including 50% contaminated sediment mixed with 50% control sediment and 100% contaminated sediment), and for 120 days to control sediment spiked with copper. We assayed changes in F(ST) (fixation index), which indicates if there is any population subdivision (i.e., structure) between the samples, expected heterozygosity, percent polymorphic loci, as well as abundance. There was a significant decrease in total abundance after 60 days in both of the 100% naturally contaminated sediments. This abundance bottleneck recovered in the Trosa treatment after 120 days but not in the Svindersviken treatment. After 120 days, there were fewer males in the 100% naturally contaminated sediments compared to the control, possibly caused by smaller size of males resulting in higher surface: body volume ratio in contact with toxic chemicals. In the copper treatment there was a significant decrease in genetic diversity after 120 days, although abundance remained unchanged. Neither of the naturally contaminated sediments (50 and 100%) affected genetic diversity after 120 days but they all had high within treatment F(ST) values, with highest F(ST) in both 100% treatments. This indicates differentiation between the replicates and seems to be a consequence of multi-toxicant exposure, which likely caused selective mortality against highly sensitive genotypes. We further assayed two growth-related measures, i.e., RNA content and cephalothorax length, but none of these endpoints differed between any of the treatments and the control. In conclusion, the results of the present study support the hypothesis that toxicant exposure can reduce genetic diversity and cause population differentiation. Loss of genetic diversity is of great concern since it implies reduced adaptive potential of populations in the face of future environmental change.

Effects of copper on the metabolism of three species of tropical oysters, Saccostrea cucullata, Crassostrea lugubris and C. belcheri

The rapid industrial development in Southeast Asia, in combination with increased population pressure, has in many places caused degradation of natural resources that many people in the region highly depend on. Attempts to evaluate environmental impacts and changes in the ecosystem due to pollution suffer from lack of data, since most knowledge about marine pollution is based on experiences from temperate areas. In the present work, physiological effects of enhanced copper concentrations on three oyster species of commercial interest were studied in laboratory experiments. Two of the species are intertidal, Saccostrea cucullata and Crassostrea lugubris, and one species is subtidal, C. belcheri. After a short-term (12 h) exposure to 20 μg copper/l, the oxygen consumption, ammonia excretion, clearance rate and absorption efficiency were measured and scope for growth calculated. The results from this study indicate that the two intertidal species are far more tolerant than the subtidal species. This is probably because they inhabit a more variable environment and have to be able to handle constantly changing environmental conditions. The subtidal habitat is normally less variable, why the copper exposure was a more severe stress, seen mainly as decreased filtration activity. The final result, i.e. changes in scope for growth, indicates that for the specific stress factor studied here, habitat selection seemed to be more important than genus.

A comparison between sites of growth, physiological performance and stress responses in transplanted Tridacna gigas

A comparison between sites of growth, physiological performance and stress responses in transplanted Tridacna gigas

Regional differences in mRNA responses in blue mussels within the Baltic proper

Mussels (Mytilus sp.) from two regions along the permanent salinity gradient within the Baltic proper were exposed to copper (35 ppb) or petrol (0.3 mL/L) for 10 days and analyzed for mRNA expressions in gill tissue. Expression of mRNAs for the heat shock proteins HSP70 and HSP90 was significantly induced by copper, but not by petrol. For the metallothioneins MT10 and MT20, regional differences in mRNA expressions could be seen. In mussels from the northern Baltic proper, MT20 expression increased 2.8 and 3.4 times, after exposure to copper and petrol, respectively. In contrast, no change could be seen in MT20 expression for mussels from the southern Baltic proper. MT10 showed a peculiar expression not previously described. For some mussels, no expression at all was detected, some showed a weak expression and for some individuals a strong expression could be seen. For the mussels from the southern Baltic proper, the number of individuals with a strong expression of MT10 increased from 1 out of 18 (control), to 7 and 8, after exposure to copper and petrol, respectively. The results clearly show that responses vary between different regions within the Baltic proper, which emphasises the importance to study interactions between contaminants, populations and regions.

Physiological responses to copper in giant clams: a comparison of two methods in revealing effects on photosynthesis in zooxanthellae.

In the present work physiological responses to a short term, sub-lethal exposure to copper (5 microg Cu2 l(-1) were studied on two species of giant clams, Tridacna gigas and Hippopus hippopus. All giant clams (fam. Tridacnidae) maintain a symbiotic relationship with photo-synthesising microalgae (zooxanthellae) and the phytotoxic effects of this copper concentration were approached with two different end points: changes in oxygen production and maximal quantum yield (Fv/Fm). Additionally we measured respiration, whereby Pg:R ratios could be calculated for the system (algae and clam) and used as an indicator of stress. Cu accumulation was only determined for T. gigas and showed significantly higher tissue concentrations in exposed specimens (11.3 microg Cu g(-1) dry wt) compared to the controls (4.2 microg Cu g(-1)). Both species displayed significantly reduced Pg:R ratios due to exposure, mainly explained by lowered gross production. No indication of stress was shown in the fluorescence measurements and possible explanations are discussed in the paper. We propose that inhibitions in the slow kinetics of photosynthesis were not captured by this fluorescence parameter. Accordingly we suggest that measurements of maximum fluorescence yield should be accompanied by complementary parameters when studying pollutants with unclear phytotoxic mechanisms.

Genetic diversity in Monoporeia affinis at polluted and reference sites of the Baltic Bothnian Bay.

The amphipod Monoporeia affinis plays an important role in the Baltic Sea ecosystem as prey and as detritivore. The species is monitored for contaminant effects, but almost nothing is known about its genetics in this region. A pilot screening for genetic variation at the mitochondrial COI gene was performed in 113 individuals collected at six sites in the northern Baltic. Three coastal sites were polluted by pulp mill effluents, PAHs, and trace metals, and two coastal reference sites were without obvious connection to pollution sources. An off-coastal reference site was also included. Contaminated sites showed lower levels of genetic diversity than the coastal reference ones although the difference was not statistically significant. Divergence patterns measured as ΦST showed no significant differentiation within reference and polluted groups, but there was significant genetic divergence between them. The off-coastal sample differed significantly from all coastal sites and also showed lower genetic variation.

Responses to temperature, heavy metal and sediment stress by the giant clam Tridacna squamosa

Increasing seawater temperature, heavy metal concentration and sediment load, all represent environmental stress factors found in the Gulf of Thailand. In the present study we investigate and compare the physiological responses of exposure to increased water temperature (+ 3°C) and copper (50 μg Cu/l) by the giant clam Tridacna squamosa, and the behavioural response to sedimentation. Both temperature and copper caused significant decrease in Pg: R ratios, although by different physiological responses. In clams exposed to copper, the decrease in Pg: R is caused by reduced photosynthesis, whereas the clams exposed to increased temperature maintained a high photosynthetic rate, but significantly increased their respiration. Clams responded to additional sediment with increased activity. This augmented activity was further increased for clams previously stressed by copper.