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31.
Sediments, marsh grasses, and ribbed mussels were collected under two CCA wood walkways (15 and 3 years old) and 1, 3, and 10 m out, in the high, middle and low marshes. These sediments, and samples from reference sites, were analyzed for Cu, Cr, and As by atomic absorption spectrophotometry. Metal concentrations were highly elevated under the walkways and up to 10 m away. Dispersal of contaminants near the old walkway was greatest in the low marsh, less in the middle, and least in the high marsh, corresponding to periods of tidal inundation. Accumulation under the walkway was generally greatest in the low marsh. Contamination was much higher in sediments under the new walkway than the old one, but metals had not dispersed as far. Accumulation patterns in plants were similar, but the contamination did not disperse as far and was not greater under the new vs the old walkway, despite differences in sediment concentrations. In mussels, bioaccumulation was seldom statistically significant, due largely to small sample sizes. 相似文献
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33.
《Limnologica》2016
The hyporheic interstitial provides habitat for many different organisms – from bacteria to burrowing invertebrates. Due to their burrowing and sediment reworking behaviour, these ecosystem engineers have the potential to affect hyporheic processes such as respiration and nutrient cycling. However, there is a lack of studies that characterize the interactions between bioturbators, physico-chemical habitat properties and microbial communities in freshwater substrates. In a standardized laboratory experiment, we investigated the effects of three functionally different bioturbators, duck mussels (Anodonta anatina, Linnaeus 1758), mayfly nymphs (Ephemera danica, Müller 1764) and tubificid worms (Tubifex tubifex, Müller 1774), on the physico-chemical conditions and bacterial communities in hyporheic substrates. We hypothesized that different invertebrates distinctly alter habitat conditions and thus microbial community composition, depending on the depth and the manner of burrowing. A. anatina and E. danica caused an increase in interstitial oxygen concentration, whereas strong declines in oxygen concentration and redox potential were detected in the T. tubifex treatment. These effects on physico-chemical habitat properties were even detectable in open water. Mussels and tubificid worms also significantly influenced the composition of bacterial communities in the hyporheic zone. A loss or replacement of bioturbators in stream ecosystems due to anthropogenic habitat alterations is expected to result in shifts in microbial community compositions, with effects on nutrient fluxes, pollutant degradation and benthic food webs. An understanding of the effects of functionally different native and invasive bioturbators is crucial to predict changes in stream ecosystem functioning. 相似文献
34.
《Limnologica》2015
Many of the unionoid mussel species are threatened, and to be able to develop strategies for effective conservation, one of the needs is to distinguish host fish species from non-host fish species using reliable methods. Margaritifera margaritifera lives as a parasite on brown trout (Salmo trutta) and/or Atlantic salmon (Salmo salar). The aim was to compare the reliability of two methods measuring the host specificity of M. margaritifera in two rivers that flow out into Skagerrak in the Atlantic Ocean. A second aim was to compare the time- and cost-efficiency of the two methods. The methods were (1) natural encystment abundances on fish in their native streams using electrofishing, and (2) encystment abundances from controlled artificial infestation in aquaria, on fish that were sacrificed. In both rivers, young-of-the-year (YOY), but not older brown trout, were naturally infested with relatively low loads of glochidia larvae, while the Atlantic salmon was not infested at all. When using artificial infestation, both YOY and older brown had encysted glochidia larvae on their gills, while glochidia larvae were not able to develop in Atlantic salmon at all. Here, the encystment was higher on the brown trout from the Lärje River, and older brown trout from the Lärje River did not seem to have as strong immunity response compared to older brown trout from the Brattefors River. In summary, brown trout is the only host fish for M. margaritifera in these rivers. Both methods can be used to discriminate between host fish species, but the method measuring natural encystment seems most time- and cost-efficient. In addition, natural encystment can be measured using a non-destructive photo-method, and is therefore suggested to be used when discriminating between host fish species for M. margaritifera. 相似文献
35.
It have been measured the denitrification rates (DR) of sediment in Saginaw Bay, Lake Huron, by N2 production method. Triplicate samples of sediment core were collected at two GLERL long-term monitoring sites of the Bay in July and August of 1995. The DR are 48.81 -24.99 and 32.81-40.51 micromol N2 -2h-1 in the Inner and Outer regions of Saginaw Bay, respectively.The characters of DR in Saginaw Bay were studied also in this paper. The DR were influenced by the interactions between the Saginaw River as a main pollution source and the Lake Huron as a reservoir of high quality water. The impacts of zebra mussels (Dreissena Polymorpha) on denitrification in Saginaw Bay, Lake Huron, were discussed, Significant differences in NH4+ exchange fluxes were detected in the inner and outer bays. The molar ratios of N2:TIN were similar at both sampling sites. Measured DR were positively correlated to O2 consumption rates in the headspace. Additionally, a negative correlation between NH4+ and NO3- concentrations in the overlying water was found. 相似文献
36.
Anita A. C. Pearson 《新西兰海洋与淡水研究杂志》2019,53(3):327-337
Interactions between two recent invaders to New Zealand, the cladocerans Daphnia galeata and D. pulex, and native filter-feeding freshwater mussels, are unknown. We examined predation rates of the common native mussel Echyridella menziesii (kākahi, kāeo) on non-native Daphnia (comparatively large zooplankton in New Zealand), relative to two common native species, the smaller cladoceran Bosmina meridionalis and rotifer Brachionus calyciflorus. Controlled laboratory experiments were conducted in which each zooplankton species was exposed to bivalve predation for a two-hour period. Comparing treatments to non-mussel controls, removal rates of non-indigenous D. pulex and native B. calyciflorus were statistically significant. Nevertheless, kākahi removal rates may not be ecologically significant for daphnids (1.7% D. galeata and 7.4% D. pulex). Kākahi removed 8.8% of B. meridionalis and 30.2% of B. calyciflorus, suggesting that small, feeble zooplankton species (particularly rotifers) are most susceptible to predation, and potentially function as an energy source for native freshwater mussels. 相似文献
37.
The mechanisms maintaining community structure following an ecosystem shift are poorly understood and we propose that they must inherently be biological. Over-exploitation can provide a “natural experiment” with man as a predator driving a change in community structure, possibly an ecosystem shift. We examined a possible mechanism that maintains algal beds as an alternative state on the east coast of South Africa where the mussel Perna perna has been overexploited. Even on unexploited shores, about 50% of mussel larvae settle onto algae, but it is unclear whether they later recruit into adult beds. On such shores we used two indirect field approaches to understand the fate of recruits, testing whether inhibition of mussel recruitment by macroalgae could constitute a biological mechanism preventing reversion from the algal to the pre-disturbance mussel-dominated state. First, we examined possible ontogenetic migration of recruits from algae to adult mussels, testing the prediction that the ratio large:small recruits in adult beds is greater where algae are liberally interspersed with mussels. Second, we examined whether, like adults, recruits show spatial structure that is related to the distribution of topographic depressions, testing the hypothesis that large and small recruits show different co-variation with depressions, microhabitats where algae commonly occur. We found no evidence that recruits on algae actively move to nearby mussel beds as neither the ratio large:small recruits nor the abundances of small or large recruits showed any relationship with algal cover/variability. Small and large recruits showed different co-variation with topographic depressions on spatially structured transects. Like adults, large recruits commonly exhibited negative relationships with depressions. Thus, large recruits neither occur on algae nor migrate from algae to the primary substratum or onto adult beds. Consequently our results (a) highlight the importance of post-settlement mortality in structuring these mussel populations, and (b) suggest that the interception of larvae by algae forms a biological mechanism that can maintain macroalgal beds that develop following exploitative disturbance by man, thus preventing or at least drastically delaying the natural recovery of mussel beds. 相似文献
38.
Carbon and nitrogen stable isotope ratios were measured in rocky inter‐tidal suspension‐feeders (brown mussels and cape reef worms) and grazers (goat's eye limpets and cape sea urchins) to determine the influences of lifestyle and time on the diets of consumers. Niche partitioning between consumer species within the same feeding guild was assessed using isotopic niche area (a proxy for trophic niche). Specimens were collected monthly at a single site in Southeastern South Africa from July 2010 to June 2011. Temporal variations in isotopic signatures were generally greater in the suspension‐feeders compared with the grazers, isotopic niche widths were smaller in the suspension‐feeders and intra‐population variations in isotope signatures were larger in the grazers. No inter‐specific niche overlap (according to standard ellipse areas) was observed within either feeding guild unless standardization calculations were used. Temporal variations in the diets of all the consumers appeared uncoupled from temporal variability in the isotopic signatures of basal resources in the region; as such, shifts in the consumer diets most likely pertained to feeding behaviour and food preferences. Our data provide new insights into how syntopic rocky shore consumers coexist by partitioning their temporally variable food environment. 相似文献
39.
刘宝银 《中国海洋大学学报(自然科学版)》1987,(3)
滩涂,是国家重点资源开发区。因此,莱州湾生物资源已引起重视。但长期以来限于常规手段难以及时进行生产潜力的估价。本研究依据卫星遥感理论与技术,应用大地卫星MSS数据监督分类,将获取的地貌类型因子量值,配合生物定量采样相关因子参数,算得莱州湾主要经济贝类资源潜力。其资源量:文蛤(Meretrix meretrix)17505吨,四角蛤蜊(Mactra veneriformis)21886吨。这不仅具有经济意义,同时也有科学意义。 相似文献
40.
On rocky shores, the relative importance of abiotic and biotic processes that regulate community structure are thought to vary with levels of shore exposure. This can lead to characteristic features found on sheltered and exposed shores. This study identified differences in the population structure of mussels on exposed and sheltered rocky shores on Atlantic coasts of south-west Ireland. Direct interactions between epibiotic algae and their host mussels were also examined to test if potential effects varied with shore exposure. Mussel beds on sheltered shores were less dense and comprised larger mussels with greater rates of individual survival and growth than those on exposed shores. The results of a field experiment showed that algal epibionts had a negative effect on mussel survival on sheltered shores but not on exposed shores. Surprisingly, the presence of algal epibionts had no effect on mussel growth on either shore type. These findings contrast with those of previous studies. The effects of shore exposure and algal epibionts on mussels may be species-specific and may interact with other factors across different regions. This study shows that predictions of effects of exposure on mussel populations and their epibionts should only be based on specific experimental evidence and cannot be generalised across regions. 相似文献