Scientific assessment of hypoxia in U.S. coastal waters

The occurrence of hypoxia, or low dissolved oxygen, is increasing in coastal waters worldwide and represents a significant threat to the health and economy of our Nation’s coasts and Great Lakes. This trend is exemplified most dramatically off the coast of Louisiana and Texas, where the second largest eutrophication-related hypoxic zone in the world is associated with the nutrient pollutant load discharged by the Mississippi and Atchafalaya Rivers. Aquatic organisms require adequate dissolved oxygen to survive. The term “dead zone” is often used in reference to the absence of life (other than bacteria) from habitats that are devoid of oxygen. The inability to escape low oxygen areas makes immobile species, such as oysters and mussels, particularly vulnerable to hypoxia. These organisms can become stressed and may die due to hypoxia, resulting in significant impacts on marine food webs and the economy. Mobile organisms can flee the affected area when dissolved oxygen becomes too low. Nevertheless, fish kills can result from hypoxia, especially when the concentration of dissolved oxygen drops rapidly. New research is clarifying when hypoxia will cause fish kills as opposed to triggering avoidance behavior by fish. Further, new studies are better illustrating how habitat loss associated with hypoxia avoidance can impose ecological and economic costs, such as reduced growth in commercially harvested species and loss of biodiversity, habitat, and biomass. Transient or “diel-cycling” hypoxia, where conditions cycle from supersaturation of oxygen late in the afternoon to hypoxia or anoxia near dawn, most often occurs in shallow, eutrophic systems (e.g., nursery ground habitats) and may have pervasive impacts on living resources because of both its location and frequency of occurrence.

The coastal environment and human health: microbial indicators, pathogens, sentinels and reservoirs

Innovative research relating oceans and human health is advancing our understanding of disease-causing organisms in coastal ecosystems. Novel techniques are elucidating the loading, transport and fate of pathogens in coastal ecosystems, and identifying sources of contamination. This research is facilitating improved risk assessments for seafood consumers and those who use the oceans for recreation. A number of challenges still remain and define future directions of research and public policy. Sample processing and molecular detection techniques need to be advanced to allow rapid and specific identification of microbes of public health concern from complex environmental samples. Water quality standards need to be updated to more accurately reflect health risks and to provide managers with improved tools for decision-making. Greater discrimination of virulent versus harmless microbes is needed to identify environmental reservoirs of pathogens and factors leading to human infections. Investigations must include examination of microbial community dynamics that may be important from a human health perspective. Further research is needed to evaluate the ecology of non-enteric water-transmitted diseases. Sentinels should also be established and monitored, providing early warning of dangers to ecosystem health. Taken together, this effort will provide more reliable information about public health risks associated with beaches and seafood consumption, and how human activities can affect their exposure to disease-causing organisms from the oceans.

Hydrogen, carbon monoxide, and methane in the marine environment

EXTRACT (SEE PDF FOR FULL ABSTRACT): The horizontal and vertical distribution of three dissolved trace gases, namely molecular hydrogen, carbon monoxide, and methane, was measured in coastal and oceanic areas. Atmospheric concentrations of these gases were measured both at locations influenced by nearby human activity, and in areas far removed from these inputs.

Interpreting long-term fish landings records: environment and/or exploitation?

The California Department of Fish and Game data base of California commercial fish landings for the period 1928 to 1985 has been assembled in computer accessible form at the Pacific Fisheries Environmental Group in Monterey, California. Time series for fishes whose landings are known to vary during periods of ocean warming were compared to time series of sea surface temperature. Expected patterns of variation were confirmed in the seasonal cycle, but were less clear on the interannual scale. When interannual variation was considered, the most serious hindrance to interpretation of the landings series appeared to be the continued reduction of the fish stocks due to commercial exploitation; other factors are discussed. Landings data contain information potentially useful in climatological studies, but problems should be anticipated in their use.

Chronic and catastrophic influences of the environment on the population dynamics of the common fishes [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Seasonal, interannual, decadal and centennial influences on population dynamics have been described for several species. It now seems possible to interpret environmental changes that initiate population change ...

Zooplankton population in the polluted environment of Thana Creek and Bombay Harbour

Hydrographical and biological parameters of Thana Creek and Bombay Harbour were studied to assess the prevailing water quality. Zooplankton samples were collected from various stations during January 1975 to July 1975. The qualitative distribution of zooplankton was found to be very irregular and fluctuating. Copepods were the dominant taxa followed by lucifers, chaetognaths, decapod larvae, ctenophores, hydromedusae, fish larvae and polychaetes. To a certain extent the distribution of zooplankton is affected by variation in salinity during different seasons, also along the length of the creek. Pronounced effect of pollution on zooplankton biomass was also observed.

Mahim Bay: a polluted environment of Bombay

Distribution of the marine life in relation to the extent of pollution at and outside Mahim Bay was studied. A poor marine fauna at stations A and B was associated with a relatively high intensity of pollution accompanied by high BOD and nutrients and low DO levels. A distinct deterioration in the marine life and water quality along the northern part of the bay as compared to the southern part was evident. An increasing trend in the marine fauna with decreasing intensity of pollution from inside to outside the bay was noticed.

Breeding of Indian major carps and common carp in semi-arid zone of Haryana under controlled environment

Vast barren lands are lying vacant in the semi-arid zone of India, which can effectively be utilised for fish farming. Experiments conducted in semi-arid conditions at Damdama indicated that it is possible to breed Indian major carps and common carp under controlled conditions of modern carps hatchery CIFE D-80 without depending on rain.

A simple technique of controlled breeding of carps in semi-arid environment

A semi-arid environment is a major constraint for production of carp seed through hypophysation. At a water temperature above 31 degree C fishes often fail to respond to induced breeding or produce partial or full eggs with fairly less fertilization, leading to their mortality during embryonic development. Field trials with Labee rohita and Cyprinus carpio communis prove that hypophysation followed by stripping and hatching in a water medium with reduced temperature (below 31 degree C) through controlled use of ice-water and water showers can result in 50-60% fertilization of eggs and 50-72% hatching for L. rohita, and 40-90% fertilization and 49-77% hatching for C. carpio communis. Simultaneous breeding experiments of the species in normal water temperature (>31 degree C) showed negative results.

Early and better maturity in carp brood stock with control of environment and feeding

Available of carp breeders in their prim state of maturity is a major constraint in hypophysation. Experiments conducted in a fish farm at Naihati, West Bengal, for two consecutive years, 1983-84 and 1984-85, clearly prove that by manipulation of environmental parameters such as metabolites, dissolved oxygen, running water conditions, as also of stock densities and quality and quantity of feed. Catla catla, Hypophythalmichthys molitrix, Labeo rohita, Cirrhina mrigala and Ctenopharyngodon idella can be made to attain better maturity and spawning stage much earlier than normal i.e. even in summer months and the entire stock spawned during the period from March to September. Percentage of successful breeding, quantities of eggs released and fertilised in relation to the body weight of all the species, were also found to be more in comparison to the brood stock raised through the conventional methods.

Heavy metals pollution in the coastal environment of Karachi

The marine environment near Karachi, particularly the Baba channel, Chari Kundi channel and Manora channel have been found contaminated with industrial effluents discharged by Malir and Lyari rivers, since they carry a high concentration of toxic heavy metals viz. Pb, Zn, Cu and Mn emanating from the industrial area and are received and discharged by the Lyari river. Out of 60 seawater samples collected from the above mentioned areas, Pb was present in 55 samples and Zn in 58 samples. The concentration of Pb was between 0.04 and 59.2ppm and the concentration of Zn was between 0.05 and 1.9ppm. Similarly all the 60 sludge samples collected from Lyari outfall and its adjoining area have been found to contain Pb and Zn in alarmingly high concentratios, which for Pb was between 15.4 and 3209.9ppm while for Zn was between 87 and 111.3ppm. Cu and Mn were also found in all the above samples.

The marked reduction of the Indus river flow downstream from the Kotry barrage: can the mangrove ecosystems of Pakistan survive in the resulting hypersaline environment?

This report deals with the application of knowledge of mangrove ecosystems from around the world to the understanding of the present status of mangroves ecosystems in Pakistan.