排序方式： 共有5条查询结果，搜索用时 171 毫秒
1
1.
A new approach for detecting and mapping sewage impacts 总被引：12，自引：0，他引：12
Costanzo SD O'Donohue MJ Dennison WC Loneragan NR Thomas M 《Marine pollution bulletin》2001,42(2):149-156
Increased nitrogen loading has been implicated in eutrophication occurrences worldwide. Much of this loading is attributable to the growing human population along the world's coastlines. A significant component of this nitrogen input is from sewage effluent, and delineation of the distribution and biological impact of sewage-derived nitrogen is becoming increasingly important. Here, we show a technique that identifies the source, extent and fate of biologically available sewage nitrogen in coastal marine ecosystems. This method is based on the uptake of sewage nitrogen by marine plants and subsequent analysis of the sewage signature (elevated delta 15N) in plant tissues. Spatial analysis is used to create maps of delta 15N and establish coefficient of variation estimates of the mapped values. We show elevated delta 15N levels in marine plants near sewage outfalls in Moreton Bay, Australia, a semi-enclosed bay receiving multiple sewage inputs. These maps of sewage nitrogen distribution are being used to direct nutrient reduction strategies in the region and will assist in monitoring the effectiveness of environmental protection measures. 相似文献
2.
This paper describes the age structure, growth, diet and aspects of gonadal development in the cobbler, Cnidoglanis macrocephalus (Valenciennes), in the large Swan estuary in south-western Australia between August 1982 and June 1984. Analysis of otolith annuli showed that while the 0+ to 3+ age classes were regularly represented in monthly samples, the 4+ and more particularly the 5+ and 6+ were much less abundant. The weighted means for the back calculated lengths at the end of the first to fourth years of life were 181 mm (≡ 26 g), 314 mm (≡ 156 g), 418 mm (≡ 410 g) and 518 mm (≡ 833 g) respectively. The mean length at the end of the second year of life was similar to the minimum legal size for capture by commercial fishermen (320 mm). The von Bertlanffy growth curve calculated from the back calculated lengths was Lt = 917 [1 − e−0·20(t + 0·11)]. The relative weight of mulluscs, crustaceans and polychaetes in the intestine varied markedly between small and large fish, apparently reflecting differences in the size of these prey. The large mean diameter of mature eggs (
) was correlated with a low mean absolute fecundity (2078). Trends shown by egg size, gonadosomatic index and time of appearance of spent females indicate that spawning takes place between October and December. The attainment of sexual maturity is both age- and size-dependent. Although sexually maturing and occasionally spent fish were found in the lower estuary, meristic values, commercial catch statistics and other data indicate that the cobbler found in the Swan estuary are part of a population which typically spawns at sea. 相似文献
3.
Evidence is presented which indicates that dense blooms of the blue-green alga Nodularia spumigena have affected fish and crab populations in a large estuarine system in south-western Australia. For example, the numbers of fish were generally very low at sites in which the chlorophyll a level, an excellent indicator of Nodularia density during the late spring and summer, was above 100 μgl?1. Moreover, commercial fishermen have recorded greatly reduced catches in Nodularia-affected areas and dead fish and crabs were found in regions where Nodularia was very dense. While the effects of this blue-green alga apparently led to death in the case of some bottom-living species in the most affected parts of the system, more active species moved into regions where Nodularia was virtually absent. 相似文献
4.
Massive increases in macroalgae (Cladophora and Chaetomorpha spp.) in the large Peel-Harvey Estuary during the 1970s, resulting from increased nutrient run-off from surrounding agricultural land, were accompanied by a marked increase in catch per unit effort (CPUE) and therefore apparently fish abundance. Despite the additional presence since the late 1970s of seasonal and extremely dense blooms of a potentially detrimental blue-green alga (Nodularia spumigena) in the Harvey Estuary, the CPUE for the whole system has also risen over recent years. However, the dense blooms of Nodularia in the Harvey Estuary greatly reduce water clarity, and also apparently fish abundance. When this occurs, Harvey Estuary fishermen shift their activities to the Peel Inlet where water clarity is far greater and they can switch from gill to haul netting, which relies on the visual detection of schools of fish. 相似文献
5.
NR Shankar Ram Chowdary V. M. Vala Venkateshwar Rao Jha Chandra Shekhar 《Theoretical and Applied Climatology》2022,148(3-4):1477-1497
Theoretical and Applied Climatology - Selection of a best suited satellite-based gridded rainfall product (SGRP) is challenging due to their significant variations at spatial and temporal scale.... 相似文献
1