RNA : DNA ratio and other nucleic acid derived indices in marine ecology

Some of most used indicators in marine ecology are nucleic acid-derived indices. They can be divided by target levels in three groups: 1) at the organism level as ecophysiologic indicators, indicators such as RNA:DNA ratios, DNA:dry weight and RNA:protein, 2) at the population level, indicators such as growth rate, starvation incidence or fisheries impact indicators, and 3) at the community level, indicators such as trophic interactions, exergy indices and prey identification. The nucleic acids derived indices, especially RNA:DNA ratio, have been applied with success as indicators of nutritional condition, well been and growth in marine organisms. They are also useful as indicators of natural or anthropogenic impacts in marine population and communities, such as upwelling or dredge fisheries, respectively. They can help in understanding important issues of marine ecology such as trophic interactions in marine environment, fish and invertebrate recruitment failure and biodiversity changes, without laborious work of counting, measuring and identification of small marine organisms. Besides the objective of integrate nucleic acid derived indices across levels of organization, the paper will also include a general characterization of most used nucleic acid derived indices in marine ecology and also advantages and limitations of them. We can conclude that using indicators, such RNA:DNA ratios and other nucleic acids derived indices concomitantly with organism and ecosystems measures of responses to climate change (distribution, abundance, activity, metabolic rate, survival) will allow for the development of more rigorous and realistic predictions of the effects of anthropogenic climate change on marine systems

RNA:DNA Ratio and Other Nucleic Acid Derived Indices in Marine Ecology

Some of most used indicators in marine ecology are nucleic acid-derived indices. They can be divided by target levels in three groups: 1) at the organism level as ecophysiologic indicators, indicators such as RNA:DNA ratios, DNA:dry weight and RNA:protein, 2) at the population level, indicators such as growth rate, starvation incidence or fisheries impact indicators, and 3) at the community level, indicators such as trophic interactions, exergy indices and prey identification. The nucleic acids derived indices, especially RNA:DNA ratio, have been applied with success as indicators of nutritional condition, well been and growth in marine organisms. They are also useful as indicators of natural or anthropogenic impacts in marine population and communities, such as upwelling or dredge fisheries, respectively. They can help in understanding important issues of marine ecology such as trophic interactions in marine environment, fish and invertebrate recruitment failure and biodiversity changes, without laborious work of counting, measuring and identification of small marine organisms. Besides the objective of integrate nucleic acid derived indices across levels of organization, the paper will also include a general characterization of most used nucleic acid derived indices in marine ecology and also advantages and limitations of them. We can conclude that using indicators, such RNA:DNA ratios and other nucleic acids derived indices concomitantly with organism and ecosystems measures of responses to climate change (distribution, abundance, activity, metabolic rate, survival) will allow for the development of more rigorous and realistic predictions of the effects of anthropogenic climate change on marine systems

Estuarine ecohydrology

Throughout the world, estuaries and coastal waters have experienced environmental degradation. Present proposed remedial measures based on engineering and technological fix have been unable to restore the ecological processes of a healthy, robust estuary and, as such, will not reinstate the full beneficial functions of the estuary ecosystem

Erasmus Mundus Master Course in Ecohydrology - an opportunity for global water education challenges

Aquatic ecosystem health has become a focus for global attention. Human population growth and climate variability are affecting both the quantity and quality of the water at a global scale. Despite the fact that Earth is the blue planet, only 3% of Earth's total water is freshwater, and only 0.03% is both accessible and suitable for human use. Estuarine and coastal ecosystems are the end points of continental discharges and pollutants, and are also being impacted by sea level rise. The recognition of the dimension of the threat led major world regions and economies to establish, often recently, protective regulations such as the Water Framework Directive in Europe (2000), the Water Law of the People's Republic of China (2002) or the Clean Water Act in the USA (1972)

MOHID as a tool to evaluate the impact of water discharge from dams on the advection of estuarine fish larval stages

The impoundment of rivers by dams is the biggest direct anthropogenic impact on the hydrological cycle. The utility of dams, as providers of water for human consumption, irrigation and electrical production, is undeniable. However, the price to pay, weighting benefits versus ecological impacts caused by dams, is enormous and often questionable. The deleterious ecological impacts caused by dams are detected at the dam’s site are and at hundreds of kilometers downstream from dams, even in estuaries and coastal areas. The uncontrolled water discharge from dams, both high volumes of water and inappropriate timing, compromise fish recruitment because eggs are flushed from estuarine spawning and nursery areas. Thus, our goal was to develop an hydrodynamic modelling approach that evaluates the impact of water discharge from dams on the advection of fish larval stages off estuaries and into coastal areas. This goal was accomplished by merging the abundance of anchovy eggs along the Guadiana estuary in MOHID

Hydrology and biota interactions as driving forces for ecosystem functioning

This chapter examines the interactions between biologic and hydrologic processes in estuarine and nearshore coastal ecosystems, and their relevance to ecosystem functioning. The role of specific hydrologic variables and processes upon key functional groups of organisms (phytoplankton, heterotrophic bacteria, holozooplankton, merozooplankton, benthos, and nekton) is addressed considering both bottom-up and top-down effects. The impact of biologic processes on relevant hydrologic features, including dissolved gases, inorganic nutrients, organic matter, chemical and biological contaminants, turbidity, and water flow, is then evaluated. Biologic-and hydrologic-driven changes are integrated, specifying how they reverberate into ecosystem functioning over different spatial and temporal scales

Macrobenthic response to sewage discharges in confined areas from coastal lagoons: implication on the ecological quality status

We studied the effect of wastewater on macrobenthic assemblages and local Ecological Quality Status (EcoQS) along a pollution gradient. The study consisted of six sampling sites surrounding the discharge channel of a Wastewater Treatment Plant located within Ria Formosa coastal lagoon. The total number of individuals was significantly higher at the discharge point comparatively to the control site, while total number of species, species richness and diversity values revealed the opposite pattern. Deposit-feeding were the most abundant trophic group, particularly at the inner sites, while the highest contributions of suspension-feeding and carnivory groups were observed at external ones. The organic matter content was positively correlated with the deposit-feeding group conferring a structural character of this variable near the plant discharge. M-AMBI index was consistent with the ANOSIM and SIMPER analysis, successfully separating the sampling stations according to the distance from the discharge and distinguishing the lower EcoQS of the inner sites not complying with the requirements of the Water Framework Directive of a “Good” quality status. In addition, changes in ecological and biotic indices were negatively correlated with variations of organic matter and positively correlated with salinity, corroborating the effect of these variables on the composition and structure of macrobenthic communities

Recovery of substrates and macro-benthos after fishing trials with a new Portuguese clam dredge

The effect of dredging on bottom structure was assessed, to estimate the damage inflicted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-fishing diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuras reached densities 8 times greater in the track region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shellfish started to rebury immediately after escaping from the dredge

Effects of hydraulic dredging on the physiological responses of the target species Chamelea gallina (Mollusca: Bivalvia): laboratory experiments and field surveys

The effects of mechanical stress in the Venus clam Chamelea gallina during hydraulic dredging were assessed in both laboratory and field studies in order to measure physiological biomarkers at organism level (clearance rate, respiration rate, scope for growth, and survival in air test)

The distribution of estuarine fish larvae: nutritional condition and co-occurrence with predators and prey

Fish larvae were collected monthly between March and September 1997 in the Mira and Guadiana estuaries (southern Portugal). Hydrological parameters were registered and zooplankton samples were obtained simultaneously. Densities of fish larvae (ind.100 m(-3)) were calculated from 211 samples and larval nutritional condition measured as RNA/DNA ratios were obtained for 346 individuals, using a fluorimetric method for nucleic acid quantification. Correlating variables were further studied using multiple regression analysis in order to assess the relative importance of abiotic and biotic factors affecting within-year trends in abundance and nutritional condition of estuarine fish larvae. Results indicated that: 1) the abundance of fish larvae seems conditioned by temperature and predation; and 2) their nutritional condition is dependent on temperature and prey availability. Temperature is an important variable structuring estuaries and therefore conditions the behaviour and physiology of fish larvae. Furthermore, the co-occurrence of predators and larvae might be related to similar feeding patterns or comensalism. Whenever feeding conditions are suitable, they usually determine enhanced growth and nutritional condition. However, predation seems to control this latter relationship through its effect on larval mortality. (C) 2000 Editions scientifiques et Medicales Elsevier SAS.info:eu-repo/semantics/publishedVersio