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Pinna bicolor (Mollusca: Pelecypoda) were transplanted between four sites near a lead smelter. The species composition of their epifauna (sessile and mobile) was examined in relation to characteristics of both sediments and seston at the sites. Seventy-two taxa were distinguished in the epifaunal community. Substantial differences were found in the short-term sensitivity of some of the species to concentrations of Cd, Pb and Zn in sediments and to sediment particle size. The short-term sensitivity of many species to metals or sediment particle size explained their long-term distribution pattern. Twenty-three taxa were identified as significantly characterizing the faunal differences. Of these, eleven (four molluscs, four bryozoans, two barnacles and one ascidian) were affected by both sediment metal concentration and particle size, and eight (four molluscs, one bryozoan, one polychaete, one hydroid and one barnacle) were affected by metal contamination but not particle size. Of all fauna examined, the Bryozoa were the most metal-sensitive. Four species, Smittina raigii (Bryozoa), Galeolaria sp. 1 (Polychaeta), Epopella simplex (Cirripedia) and Monia ione (Pelecypoda) were identified by their short- and long-term sensitivity to metal contamination, and absence of sensitivity to sediment particle size, as suitable species for monitoring the effects of metal contamination on the epifauna. The implications of the results for toxicity-testing are discussed. 相似文献
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Adam Toma&#x;ových Ivo Gallmetzer Alexandra Haselmair Darrell S. Kaufman Borut Mavri
Martin Zuschin 《Sedimentology》2019,66(3):781-807
Carbonate sediments in non‐vegetated habitats on the north‐east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand‐dwelling Gouldia minima and opportunistic Corbula gibba are time‐averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co‐occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre‐scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top‐core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft‐bottom vegetated zones and hard‐bottom Arca beds) and present‐day oligophotic communities with organic‐loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats. 相似文献
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南麂列岛邻近海域贝类生态分布的初步研究 总被引：7，自引：0，他引：7
对南麂列岛邻近海域贝类生态分布的初步研究表明,在该海域共发现贝类４２种,广温广布种占５２．４％,亚热带种占２８．５％,热带种和暖温带种各占１１．９％和７．１％。优势种有江户明樱蛤Ｍｏｅｒｅｌａｊｅｄｏｅｎｓｉｓ、圆筒原盒螺Ｅｏ－ｃｙｌｉｃｈｎａｃｙｌｉｎｄｒｅｌａ、经氏壳蛞蝓Ｐｈｉｌｉｎｅｋｉｎｇｌｉｐｉｎｉ等。春、秋两季平均生物量为４．４０ｇ／ｍ２,平均栖息密度为５７．２６个／ｍ２,数量分布不均匀,并有明显季节变化。种类和数量变动与海流、温度、盐度、潮流、底质等因子有关。 相似文献
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Miguel P. Sastre 《Estuarine, Coastal and Shelf Science》1984,19(2):217-230
Donax denticulatus population density and size distribution were studied in five different Puerto Rican beaches for a one year period in order to determine relationships between the densities and size distributions of the clam, and twelve different physico-chemical parameters of sediments and water. Maní beach exhibits significantly higher population densities followed by Luquillo, Esperanza and Ballenas. No clams were found in Crashboat. Luquillo and Esperanza had similar population fluctuations, having peak densities in August and January. Maní had higher densities in September and May, and Ballenas in June. The only major settlement period appeared during January at Esperanza. The bigger clams (30 mm) were found in Maní only. Higher population density and bigger clams in Maní are related to waters having high concentrations of total organic carbon, particulate organic carbon and nitrates. The clam was absent from Crashboat where very low levels of phosphates and nitrates were observed. These studies indicate relationships between water and sediment quality, and densities of D. denticulatus. 相似文献
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Light‐adapted eyes of two freshwater gastropods with similar habitat preferences (Latia neritoides (Gray 1850) and Ancylus fluviatilis (Müller 1774)) were compared with each other in relation to optics, anatomy, and ultrastructure. Individuals of L. neritoides not only possess significantly larger eyes than similarly sized A. fluviatilis, they also have a more voluminous layer of photorecep‐tive membranes and appear capable of discerning at least some crude shapes. The eye of A. fluviatilis, on the other hand, has a very shallow retina which is so closely apposed to the lens that it can be little more than an indicator of light and darkness. Both types of eye are generously endowed with screening pigment granules and exhibit no signs of light‐induced damage. Although the lenticular F‐values for L. neritoides (1.78) and A. fluviatilis (1.74) alone are hardly indicative of an adaptation to a dark environment, the greater amount of photic vesicles and the substantial development of muscle fibres in the eye of L. neritoides suggest that the latter can adjust its vision more rapidly to changing light levels than that of A. fluviatilis. Since L. neritoides (but not A. fluviatilis) has the ability to secrete a bright green luminescent mucus, a faster accommodation system would serve the species well. There is, however, no proof that in Latia bioluminescence alone has been responsible for the development of a more capable eye. Most of the differences between the eyes of L. neritoides and A. fluviatilis can be explained by the distinctly greater nocturnal activity of L. neritoides in combination with the ability to produce bright light in the latter species. 相似文献
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E.N. Powell H. Cummins R.J. Stanton G. Staff 《Estuarine, Coastal and Shelf Science》1984,18(4):367-384
The death assemblage is an important source of information about temporal variability in community composition. The living community and the short-term death assemblage have been studied at a sandy-bottom station in the Laguna Madre, Texas. Abundance peaks of living species are usually followed by long-term abundance increases of the same species in the death assemblage. This phenomenon provides a tool for investigating between-sampling-occasion events in the preservable component of the living community. Given a six-week sampling regimen, approximately 90% of all individuals settle, live and die during the period between consecutive sampling occasions and are not collected alive. Thus, larval settlements are consistently underestimated by about 90% from data on the living community. Comparisons of year-to-year variability in settlement and survivorship of settled individuals in the youngest age classes may be considerably in error. Better estimations of actual settlement and survivorship can be made from the death assemblage provided that the rate of taphonomic loss can be quantified. The rate of taphonomic loss can be expressed as the species' half-life, the time required for the destruction of 50% of the individuals that were added to the death assemblage following settlement. Half-lives for the smallest size classes in the death assemblage at this site are about 100 days. 相似文献
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重论真马(Equus属)首次出现可作为第四纪下限的标志 总被引：1，自引：0，他引：1
真马（Ｅｑｕｕｓ属）首次出现曾被作为第四纪下限标志，近年来不断受到怀疑、甚至否定。然而，根据目前公认的２．５ＭａＢ．Ｐ．的第四纪下限，则真马在欧亚大陆的首次出现正与此界线吻合，从欧洲维拉方动物群、中国北方泥河湾地层、南方元谋盆地，以及其他剖面得到的证据都证明了这一点。真马首次出现事件与２．５ＭａＢ．Ｐ．的许多重大地质事件同时，如古地磁高斯期与松山期界线，中国黄土开始堆积、北极冰盖出现、新构造运动第一次强化等。真马首次出现于２．５ＭａＢ．Ｐ．是由于北极冰盖出现所伴随的海平面下降，导致白令海峡露出水面，欧亚大陆和北美大陆得以连通，在北美起源并在进化上取得成功的真马迅速扩散至欧亚大陆等地。因此，真马首次出现可以作为这些地区第四纪下限的一个显著标志，尤其是在欧亚大陆。 相似文献