Marine and Freshwater Research 

About: Marine and Freshwater Research is an academic journal published by CSIRO Publishing. The journal publishes majorly in the area(s): Population & Estuary. It has an ISSN identifier of 1323-1650. Over the lifetime, 5449 publications have been published receiving 170865 citations. The journal is also known as: Marine and freshwater research.

Climate change, coral bleaching and the future of the world's coral reefs

Abstract: Sea temperatures in many tropical regions have increased by almost 1 degrees C over the past 100 years, and are currently increasing at similar to 1-2 degrees C per century. Coral bleaching occurs when the thermal tolerance of corals and their photosynthetic symbionts (zooxanthellae) is exceeded. Mass coral bleaching has occurred in association with episodes of elevated sea temperatures over the past 20 years and involves the loss of the zooxanthellae following chronic photoinhibition. Mass bleaching has resulted in significant losses of live coral in many parts of the world. This paper considers the biochemical, physiological and ecological perspectives of coral bleaching. It also uses the outputs of four runs from three models of global climate change which simulate changes in sea temperature and hence how the frequency and intensity of bleaching events will change over the next 100 years. The results suggest that the thermal tolerances of reef-building corals are likely to be exceeded every year within the next few decades. Events as severe as the 1998 event, the worst on record, are likely to become commonplace within 20 years. Most information suggests that the capacity for acclimation by corals has already been exceeded, and that adaptation will be too slow to avert a decline in the quality of the world's reefs. The rapidity of the changes that are predicted indicates a major problem for tropical marine ecosystems and suggests that unrestrained warming cannot occur without the loss and degradation of coral reefs on a global scale.

How much wetland has the world lost? Long-term and recent trends in global wetland area

Abstract: It has been frequently stated, but without provision of supporting evidence, that the world has lost 50% of its wetlands (or 50% since 1900 AD). This review of 189 reports of change in wetland area finds that the reported long-term loss of natural wetlands averages between 54–57% but loss may have been as high as 87% since 1700 AD. There has been a much (3.7 times) faster rate of wetland loss during the 20th and early 21st centuries, with a loss of 64–71% of wetlands since 1900 AD. Losses have been larger and faster for inland than coastal natural wetlands. Although the rate of wetland loss in Europe has slowed, and in North America has remained low since the 1980s, the rate has remained high in Asia, where large-scale and rapid conversion of coastal and inland natural wetlands is continuing. It is unclear whether the investment by national governments in the Ramsar Convention on Wetlands has influenced these rates of loss. There is a need to improve the knowledge of change in wetland areas worldwide, particularly for Africa, the Neotropics and Oceania, and to improve the consistency of data on change in wetland areas in published papers and reports.

Methods of Assessing Ovarian development in Fishes: a Review

Abstract: An important component of many studies of fish reproductive biology is the assessment of the stage of gonad development of individual fish. The methods in use vary from highly detailed to cursory, but there are few reviews of their reliability or usefulness. This review examines histology, measurements of oocyte size, staging based on the appearance of whole oocytes, staging based on the external appearance of the ovary, and gonad indices. Histology is the most accurate technique, but it is time- consuming and expensive. Staging based on the appearance of whole oocytes can be a useful alternative but may be inaccurate with oocytes in transitional stages of development. Staging based on the external appearance of the ovary is the simplest and most rapid method, but it may be subjective and its accuracy is uncertain. Oocyte size may be used as a predictor of developmental stage if the size ranges of the various stages are known, but the sizes of different oocyte stages may overlap, which complicates this approach. Oocyte size may be used on its own to measure development but gives little information on the physiological status of the ovaries. Gonad indices (gonad size relative to body size) provide a useful insight into changes in ovary size and complement results obtained using staging methods. However, gonad indices, like oocyte size, may be biased when samples of fish of different body sizes are compared.

Flow variability and the ecology of large rivers

Abstract: Ecological processes in large rivers are controlled by their flow variability. However, it is difficult to find measures of hydrological variability that characterize groups of rivers and can also be used to generate hypotheses about their ecology. Multivariate analyses of the hydrographs of 52 rivers worldwide revealed distinctive patterns of flow variability that were often correlated with climate. For example, there were groups of rivers that corresponded broadly with ‘tropical’ and ‘dryland’ climates. However, some rivers from continental climates occupy both extremes of this range, illustrating the limitations of simple classification. Individual rivers and groups of rivers may also have different hydrographic ‘signatures’, and attempts to combine measures of hydrological variability into indices mask biologically significant information. This paper identifies 11 relatively independent measures of hydrological variability that help categorize river types and are each associated with aspects of fish biology. Ways are suggested by which the Flood Pulse Concept can be expanded to encompass hydrological variability and accommodate differences among groups of rivers from different climatic regions. Such recognition of the complex role of hydrological variability enhances the value of the concept for river conservation, management and restoration.

Beyond BACI: Experimental designs for detecting human environmental impacts on temporal variations in natural populations

Abstract: Biological effects of environmental impacts are usually defined simplistically in terms of changes in the mean of some biological variable. Many types of impact do not necessarily change long-run mean abundances. Here, designs for detection of environmental impact are reviewed and some of their shortcomings noted. New sampling designs to detect impacts that cause changes in temporal variance in abundance of populations, rather than their means, are described. These designs are effective at distinguishing pulse and press episodes of disturbance and could be used for other variables of interest (size, reproductive state, rate of growth, number of species, etc.) for monitoring. The designs require sampling different time-scales before and after a proposed development that might cause impact. Cases are discussed in which there is a single control location. Inadequacies of this approach for detection of environmental impact are mentioned, with some discussion of the consequences for management of impacts that cause temporal change rather than alterations of the mean abundance of a population.