Recovery in aquatic ecosystems: an overview of knowledge and needs

This article summarizes the views of scientists asked to address some of the critical unanswered questions concerning recovery in aquatic systems. Spatial and temporal variability were emphasized because of their implications for our abilities to distinguish between recovered and non-recovered ecosystems and the consequent effects such variability has on the statistical precision of developed recovery metrics. There was also consensus that pre-disturbance ecosystem states may not be re-established in the absence of a disturbance event and that better data sets will be required to separate the influences of natural variability from disturbance event induced fluctuations in many biological measures. Although discussions tended to focus at the population or community level, evidence from physiological-based measures of recovery indicates divergent rates of recovery at varying levels of biological organization, a fact which suggests a role for biomarkers in developing a complete understanding of recovery. Critical questions concerning the determination and understanding of recovery that remain to be answered are identified. This revised version was published online in July 2006 with corrections to the Cover Date.     

Environmental constraints upon locomotion and predator-prey interactions in aquatic organisms: an introduction

Environmental constraints in aquatic habitats have become topics of concern to both the scientific community and the public at large. In particular, coastal and freshwater habitats are subject to dramatic variability in various environmental factors, as a result of both natural and anthropogenic processes. The protection and sustainable management of all aquatic habitats requires greater understanding of how environmental constraints influence aquatic organisms. Locomotion and predator-prey interactions are intimately linked and fundamental to the survival of mobile aquatic organisms. This paper summarizes the main points from the review and research articles which comprise the theme issue 'Environmental constraints upon locomotion and predator-prey interactions in aquatic organisms'. The articles explore how natural and anthropogenic factors can constrain these two fundamental activities in a diverse range of organisms from phytoplankton to marine mammals. Some major environmental constraints derive from the intrinsic properties of the fluid and are mechanical in nature, such as viscosity and flow regime. Other constraints derive from direct effects of factors, such as temperature, oxygen content of the water or turbidity, upon the mechanisms underlying the performance of locomotion and predator-prey interactions. The effect of these factors on performance at the tissue and organ level is reflected in constraints upon performance of the whole organism. All these constraints can influence behaviour. Ultimately, they can have an impact on ecological performance. One issue that requires particular attention is how factors such as temperature and oxygen can exert different constraints on the physiology and behaviour of different taxa and the ecological implications of this. Given the multiplicity of constraints, the complexity of their interactions, and the variety of biological levels at which they can act, there is a clear need for integration between the fields of physiology, biomechanics, behaviour, ecology, biological modelling and evolution in both laboratory and field studies. For studies on animals in their natural environment, further technological advances are required to allow investigation of how the prevailing physico-chemical conditions influence basic physiological processes and behaviour.     

Genetic studies in relation to kuru: an overview

Kuru is a subacute neurodegenerative disease presenting with limb ataxia, dysarthria, and a shivering tremor. The disease progress to complete motor and mental incapacity and death within 6 to 24 months. Neuropathologically, a typical pattern of neuronal loss, astrocytic and microglial proliferation, characteristic "kuru-type" amyloid plaques, and PrP deposits in the cerebral cortex and cerebellum are observed. Kuru is the prototype of a group of human transmissible spongiform encephalopathies (TSEs), or "prion" diseases, that include hereditary, sporadic and infectious forms. The latest member of this group, the variant Creutzfeldt-Jakob disease (vCJD), linked to transmission of bovine spongiform encephalopathy (BSE) to humans, shows features similar to kuru. Kuru has emerged at the beginning of the 1900s in a small indigenous population of New-Guinean Eastern Highlands, reached epidemic proportions in the mid-1950s and disappeared progressively in the latter half of the century to complete absence at the end of the 1990s. Early studies made infection, the first etiologic assumption, seem unlikely and led to a hypothesis that kuru might be a genetically determined or genetically mediated illness. After transmissibility of kuru had been discovered and all major epidemiologic phenomena adequately explained by the spread of an infectious agent with long incubation period through the practice of cannibalism, the pattern of occurrence still continued to suggest a role for genetic predisposition. Recent studies indicate that individuals homozygous for Methionine at a polymorphic position 129 of the prion protein were preferentially affected during the kuru epidemic. The carriers of the alternative 129Met/Val and 129Val/Val genotypes had a longer incubation period and thus developed disease at a later age and at a later stage of the epidemic. Observations made during the kuru epidemic are helpful in the understanding of the current vCJD outbreak, and vice versa clinical and experimental data accumulated in studies of other TSE disorders contribute to better understanding of the documented kuru phenomena.     

Behavioural studies on eriophyoid mites: an overview

Eriophyoid mites are excellent candidates for ethological research using the approaches of behavioural ecology and sociobiology. These tiny haplodiploid mites are highly specialized plant parasites, producing galls, forming nests, inhabiting refuges or living freely on plants. They reproduce via spermatophores deposited on a substrate and without pairing, which is a fascinating, though still poorly understood, mode of reproduction widespread in some groups of arthropods. Eriophyoid males can be involved in external sperm competition. In some species they also guard pre-emergent females and deposit spermatophores beside them. Although slow-walking, the minute eriophyoid mites can disperse for long distances on air currents or specific animal carriers. After landing on a plant they can distinguish between suitable and unsuitable hosts. Biological observations on a deuterogynous species indicate that parasociality could occur among eriophyoid mites. Many eriophyoids are of economic importance. Knowledge of their behaviour may promote understanding their ecology, may resolve problems in their phylogeny and may help developing methods for their control. In this paper, attention is directed to dispersal modes of eriophyoid mites, their feeding and host acceptance, spermatophore deposition and mating, defence against predators, and social behaviour.     

Effect of nanoparticles on aquatic organisms

This paper summarizes the data on the effect of engineered nanoparticles on aquatic organisms. The issues of penetration and accumulation of nanoparticles in the body of aquatic organisms and their toxic effect, biotransformation, and migration along food webs are considered. It is demonstrated that the behavior of nanomaterials in the environment and their effect on living organisms have been studied insufficiently and require close attention, because their release into the environment will increase in the very near future.     

Species studies in sea ranching: an overview and economic perspectives

Reviews in Fish Biology and Fisheries -     

Dispersal of aquatic organisms by waterbirds: a review of past research and priorities for future studies

1. Inland wetlands constitute ecological islands of aquatic habitat often isolated by huge areas of non-suitable terrestrial habitats. Although most aquatic organisms lack the capacity to disperse by themselves to neighbouring catchments, many species present widespread distributions consistent with frequent dispersal by migratory waterbirds.
2. A literature review indicates that bird-mediated passive transport of propagules of aquatic invertebrates and plants is a frequent process in the field, at least at a local scale. Both endozoochory (internal transport) and ectozoochory (external transport) are important processes.
3. The characteristics of the dispersed and the disperser species that facilitate such transport remain largely uninvestigated, but a small propagule size tends to favour dispersal by both internal and external transport.
4. We review the information currently available on the processes of waterbird-mediated dispersal, establishing the limits of current knowledge and highlighting problems with research methods used in previous studies. We also identify studies required in the future to further our understanding of the role of such dispersal in aquatic ecology.     

Bioactive peptides from marine organisms: a short overview

Marine organisms are an immense source of new biologically active compounds. These compounds are unique because the aqueous environment requires a high demand of specific and potent bioactive molecules. Diverse peptides with a wide range of biological activities have been discovered, including antimicrobial, antitumoral, and antiviral activities and toxins amongst others. These proteins have been isolated from different phyla such as Porifera, Cnidaria, Nemertina, Crustacea, Mollusca, Echinodermata and Craniata. Purification techniques used to isolate these peptides include classical chromatographic methods such as gel filtration, ionic exchange and reverse-phase HPLC. Multiple in vivo and in vitro bioassays are coupled to the purification process to search for the biological activity of interest. The growing interest to study marine natural products results from the discovery of novel pharmacological tools including potent anticancer drugs now in clinical trials. This review presents examples of interesting peptides obtained from different marine organisms that have medical relevance. It also presents some of the common methods used to isolate and characterize them.     

Threats, management and envisaged utilizations of aquatic weed Eichhornia crassipes: an overview

Eichhornia crassipes or water hyacinth is a free-floating plant, growing plentifully in the tropical water bodies. This invasive weed poses multiple hazards ranging from ecological and economical to social. It tends to endanger biodiversity, cause eutrophication, shelter pests, clog fresh waterways, affect agriculture and aquaculture, hamper shipping and recreational activities. Existing control methods have been insufficient to contain its aggressive propagation. Recently, it has been envisaged that successful utilization of this weed can solve the associated problems associated with them. It is being speculated that the huge biomass can be used in waste water treatment, heavy metal and dye remediation, as substrate for bioethanol and biogas production, electricity generation, industrial uses, human food and antioxidants, medicines, feed, agriculture and sustainable development. Towards this quest many approaches have been undertaken and partial success is achieved. If harnessed properly, this weed-based green technology can solve many of the issues our society faces now. In this context, the papers published in recent years have been reviewed, with the objective of creating public awareness and bolstering management and utilization of this cumbersome invasive weed.     

Solar ultraviolet radiation-induced DNA damage in aquatic organisms: potential environmental impact

Continuing depletion of stratospheric ozone and subsequent increases in deleterious ultraviolet (UV) radiation at the Earth's surface have fueled the interest in its ecological consequences for aquatic ecosystems. The DNA is certainly one of the key targets for UV-induced damage in a variety of aquatic organisms. UV radiation induces two of the most abundant mutagenic and cytotoxic DNA lesions, cyclobutane pyrimidine dimers (CPDs) and pyrimidine pyrimidone photoproducts (6-4PPs) and their Dewar valence isomers. However, aquatic organisms have developed a number of repair and tolerance mechanisms to counteract the damaging effects of UV on DNA. Photoreactivation with the help of the enzyme photolyase is one of the most important and frequently occurring repair mechanisms in a variety of organisms. Excision repair, which can be distinguished into base excision repair (BER) and nucleotide excision repair (NER), also play an important role in DNA repair in several organisms with the help of a number of glycosylases and polymerases, respectively. In addition, mechanisms such as mutagenic repair or dimer bypass, recombinational repair, cell-cycle checkpoints, apoptosis and certain alternative repair pathways are also operative in various organisms. This review deals with the UV-induced DNA damage and repair in a number of aquatic organisms as well as methods of detecting DNA damage.     

Population studies of three aquatic gastropods in an intermittent backwater

Summary Three snail populations of an intermittent backwater were studied over a 20-month period, and estimates were made of rate of population change, mean biomass, annual and summer net production, and survival under conditions of little standing water. Lymnaea palustris and Physa integra populations were essentially univoltine, while G. parvus appeared to produce several generations during the year. L. palustris formed a protective epiphragm and was apparently better suited to recurrent dry periods than either G. parvus or P. integra, the latter population being maintained through immigration from the stream population. The population density of G. parvus was usually well below, and more aggregated, than the other two species, and there was considerable sampling error associated with its estimated population parameters.The estimated annual production rates for L. palustris and P. integra were 2.18 g/m² and 1.59 g/m², respectively, and these two species accounted for about 98% of the total gastropod production. About 75.9% and 66.5% of the L. palustris and P. integra production, respectively, occurred between June and November. Summer turnover ratios (ratio of production to mean standing crop) in 1969 were 4.69 for L. palustris and 2.94 for P. integra. An extended dry period early in the summer of 1970 reduced total snail production to about 18–24% that of the previous season, although summer turnover ratios were fairly consistent.     

New methods for quantitative and qualitative facial studies: an overview

The clinical study of birth defects has traditionally followed the Gestalt approach, with a trend, in recent years, toward more objective delineation. Data collection, however, has been largely restricted to measurements from X-rays and anthropometry. In other fields, new techniques are being applied that capitalize on the use of modern computer technology. One such technique is that of remote sensing, of which photogrammetry is a branch. Cartographers, surveyors and engineers, using specially designed cameras, have applied geometrical techniques to locate points on an object precisely. These techniques, in their long-range application, have become part of our industrial technology and have assumed great importance with the development of satellite-borne surveillance systems. The close-range application of similar techniques has the potential for extremely accurate clinical measurement. We are currently evaluating the application of remote sensing to facial measurement using three conventional 35 mm still cameras. The subject is photographed in front of a carefully measured grid, and digitization is then carried out on 35-mm slides specific landmarks on the cranioface are identified, along with points on the background grid and the four corners of the slide frame, and are registered as xy coordinates by a digitizer. These coordinates are then converted into precise locations in object space. The technique is capable of producing measurements to within 1/100th of an inch. We suggest that remote sensing methods such as this may well be of great value in the study of congenital malformations.     

Lectins of living organisms. The overview

Occurrence, organization, and functioning of lectins as well as their current classifications are under investigation. Results indicate importance of symbiotic lectins for clinical microecology. Lectins and lectin-based approaches have wide perspectives for medical biotechnology. Lectin terms, relationships between lectins and enzymes are discussed.     

Effects of contaminants on genetic patterns in aquatic organisms: a review.

There is increasing awareness of the need to evaluate the effects of contaminants at the population level. Genetic techniques offer a powerful approach to assess contaminant-induced changes in populations. Yet studies to date are relatively few and not always carefully designed to maximize the utility inherent in this approach. We present a summary of contemporary genetic assessment methods and a review of published studies of genetic effects in field-exposed aquatic organisms. We discuss evaluations of genetic patterns that use genetic adaptation, allozyme variation, and molecular genetic (DNA) variation. Direct tests of genetic adaptation are very effective in establishing a concrete, and potentially deleterious population-level effect of contaminant exposure, but they are difficult to accomplish with most field-exposed organisms. Allozyme surveys are relatively simple and common, and may provide data that are suggestive of contaminant effects. However, these are rarely conclusive, primarily because few allozyme loci are variable and these few loci represent extremely small portions of the genome. Molecular genetic techniques have the potential to be very effective. But, there is a tendency to emphasize the power of the techniques, rather than the underlying causes of the molecular genetic patterns observed. The strength of the conclusions of each study varies widely, partially derived from variation in the strength of the techniques. We caution that all these approaches are greatly improved by careful experimental design that includes adequate numbers of reference and contaminated sites and sample size. In addition, careful exposure assessment is required, including site and tissue chemistry, biomarker responses, and measures of potentially deleterious effects, such as DNA damage, or reduced reproductive output or survival.     

Some remarks on ecological groups of aquatic organisms

An analysis of several publications discussing versions of the conception of ecological groups of aquatic organisms in mountain streams and overgrowths of higher aquatic plants has been performed.     

Energy costs of carbon dioxide concentrating mechanisms in aquatic organisms

Minimum energy (as photon) costs are predicted for core reactions of photosynthesis, for photorespiratory metabolism in algae lacking CO₂ concentrating mechanisms (CCMs) and for various types of CCMs; in algae, with CCMs; allowance was made for leakage of CO₂ from the internal pool. These predicted values are just compatible with the minimum measured photon costs of photosynthesis in microalgae and macroalgae lacking or expressing CCMs. More energy-expensive photorespiration, for example for organisms using Rubiscos with lower CO₂–O₂ selectivity coefficients, would be less readily accommodated within the lowest measured photon costs of photosynthesis by algae lacking CCMs. The same applies to the cases of CCMs with higher energy costs of active transport of protons or inorganic carbon species, or greater allowance for significant leakage from the accumulated intracellular pool of CO₂. High energetic efficiency can involve a higher concentration of catalyst to achieve a given rate of reaction, adding to the resource costs of growth. There are no obvious mechanistic interpretations of the occurrence of CCMs algae adapted to low light and low temperatures using the rationales adopted for the occurrence of C₄ photosynthesis in terrestrial flowering plants. There is an exception for cyanobacteria with low-selectivity Form IA or IB Rubiscos, and those dinoflagellates with low-selectivity Form II Rubiscos, for which very few natural environments have high enough CO₂:O₂ ratios to allow photosynthesis in the absence of CCMs.     

Calmodulin: an overview

Calmodulin is a 16,700-dalton Ca2+-binding protein ubiquitous in the eukaryotes. It has no intrinsic enzymatic activity, but it regulates a wide spectrum of enzymes that control many basic cellular processes, ranging from the metabolism of cyclic nucleotides, Ca2+, and glycogen to contractile activity and stimulus-secretion coupling. Mounting evidence now indicates that calmodulin is the major intracellular Ca2+ receptor that remained elusive despite three decades of extensive work by many investigators.