Hydrobiological Bulletin

Government policy in the Netherlands aims at reducing phosphate inputs into surface waters by (I) adding phosphate removal facilities to sewage treatment plants, and (II) simultaneously banning phosphates from detergents. Several reasons are given for the necessity of detergent phosphate banning: reasons of environmental requirements and cost, but also of public acceptance. Four alternatives to phosphate are discussed briefly: soap, Citrex-S5, NTA (nitrilo-triacetic acid), and zeolites. All four are available in the Netherlands, as are detergent formulations containing them. In a simplified comparative assessment of environmental properties of phosphate substitutes and phosphate itself, the substitutes appear relatively safe. In January 1980 the results of a detailed environmental assessment of phosphate substitutes have been published, together with the text of an agreement between government and detergent manufacturers on a phosphate reduction program for the next three years.

Tại châu Âu, có sự chú ý mới về mối quan hệ giữa các chỉ tiêu hóa học và tác động sinh thái do Khuôn khổ nước (Water Framework Directive - WFD). Trong bài báo này, chúng tôi sử dụng phân tích hồi quy để kiểm tra mối quan hệ giữa nồng độ trung bình chlorophyll a trong mùa sinh trưởng với tổng phốt pho và tổng nitơ, sử dụng dữ liệu tóm tắt từ hơn 1.000 hồ ở châu Âu. Để phân tích, các hồ được chia thành các loại với ba loại độ sâu trung bình, độ kiềm và hàm lượng humic. Các hồ cũng được chia thành các vùng địa lý rộng, bao gồm các khu vực Đại Tây Dương, Bắc Âu, Trung Âu/Baltic và ở một số loại hồ là khu vực Địa Trung Hải ở châu Âu. Chlorophyll a được phát hiện có mối liên hệ đáng kể với cả tổng phốt pho và tổng nitơ, mặc dù tổng phốt pho gần như luôn được xác định là yếu tố dự đoán tốt nhất cho chlorophyll. Các mối quan hệ giữa chất dinh dưỡng và chlorophyll khác nhau được tìm thấy cho các hồ tùy theo độ sâu trung bình và độ kiềm, tuy nhiên không tìm thấy ảnh hưởng đáng kể nào của vùng địa lý hoặc hàm lượng humic đối với hầu hết các loại hồ. Chúng tôi xác định được ba nhóm hồ có phản ứng khác biệt đáng kể. Các hồ sâu cho thấy sản lượng chlorophyll thấp nhất trên mỗi đơn vị dinh dưỡng, trong khi các hồ nông có độ kiềm thấp và trung bình cho thấy sản lượng cao nhất, và các hồ có độ kiềm cao có phản ứng ở mức trung bình. Chúng tôi khuyến nghị rằng các mô hình hồi quy được cung cấp cho ba nhóm hồ này nên được sử dụng cho quản lý hồ ở châu Âu và thảo luận về những hạn chế của các mô hình như vậy.

Daphnia hyalina × galeata in Castelo-do-Bode Reservoir was regulated mainly by food availability during the summers of 1993 and 1994. Because of high temperatures and low rainfall in 1994, the reservoir was, apparently, more eutrophic relatively to 1993. Higher chlorophyll-a concentrations and higher clutch size in 1994 suggest that Daphnia population benefited from better feeding conditions in 1994. The analysis of the contributions from fecundity and adult proportion to birth rate variation suggest that vertebrate predation and predation by copepods were negligible factors as population organisers. A general decrease in the abundance of large crustaceans during the periods of high density of typhloplanid flatworms, in both years, points to the importance of flatworm predation on zooplankton. A decrease in the number of individuals in all Daphnia size classes was observed during the periods of flatworms population increase.

The Fucus populations on rocky shores along 300 km of the coastal waters of southeast Sweden in the Baltic proper have been studied since 1984 at a number of fixed sites as part of monitoring programmes. This paper describes changes in distribution and abundance of F. vesiculosus and F. serratus during the period 1984–2001. Sheltered sites showed a consistent temporal and spatial pattern of Fucus spp. distribution over a coastline of 300 kilometres. The depth penetration and abundance of Fucus spp. increased during the 1980s. Around 1990 the development reversed as a consequence of grazing and in 1997 many sites were almost devoid of Fucus spp. Since 1998 both abundance and depth penetration have increased again, possibly as a result of local measures against eutrophication. Exposed sites, on the other hand, lost their Fucus populations at the beginning of the 1990s, and they have not recovered. Extended field studies lead us to deduce that the fixed sites referred to above were representative of the Fucus populations in the area investigated. Major declines, both at sheltered and exposed sites, are attributed to grazing by the isopod Idotea baltica. The populations of I. baltica may have been favoured by the continuing eutrophication of the Baltic, a series of mild winters in the 1990s, and a contemporary decline in some potential predators.

Stormwater retention ponds receive a variety of urban and highway pollutants that may have adverse effects on water-dwelling organisms. In this exploratory study, the benthic diatom community composition at genus level of nine such ponds servicing highway, residential, industrial, and mixed industrial/residential catchments was examined. Thirteen biocides were measured in the pond water as one of the possible explanatory factors for diatom taxonomic variability. The uppermost 1 cm of sediment was sampled, and a total of 50 diatom genera were identified. Moderate to high similarities were found among the diatom communities of the ponds. Two genera, namely Navicula and Nitzschia, were the most abundant and accounted for 19–47% of the relative abundance in the ponds. Estimated relative abundances of diatom genera and measured biocide concentrations in the ponds were grouped according to land use. Highway ponds were found to be significantly different from ponds servicing residential and industrial catchments, while no significant differences were found between residential and industrial ponds. The presence of biocides alone could not explain diatom taxonomic variability, although some evidence was found that communities differed depending on the catchment type of the ponds. The results of this exploratory study are an important contribution to future works investigating stormwater diatom communities, where combined effects of biocides and other stormwater contaminants and community stressors, e.g., metals, PAHs, road salt, should be explicitly looked at.

The intertidal and subtidal soft-sediment macrofauna of the upper Forth estuary, eastern Scotland, UK has been examined. The intertidal fauna was sampled in 1977, and again in 1988/89, at up to twelve stations along the salinity gradient. The subtidal fauna was sampled in 1982 and in 1988/89 at up to 15 stations. The stations span the region of the freshwater-seawater interface, and area of the turbidity maximum. Large spatial and temporal variations in macrofaunal abundance and species composition were observed. Sites at the head of the estuary with low salinity were dominated by oligochaetes, but more saline areas were characterised by a depauparate estuarine fauna. The area has historically received large quantities of organic waste both from sewage and industrial discharges which supported very high abundances of oligochaetes of up to 500,000 m−2 in the upper reaches of the estuary. Reductions in the organic inflow to the area since the early-1980's have begun to cause reductions in oligochaete populations and also allowed the further penetration intertidally of non-oligochaete species into the upper and middle reaches of the estuary. No comparable upstream penetration by the non-oligochaete subtidal fauna has been observed, possibly on account of the greater sediment instability in the estuary's main channel.