Search

This paper intends to show how the radio frequency-electromagnetic (RF-EM) method can be successfully used in coastal wetlands, onshore and in shallow water. It characterizes and reveals geological and hydrogeological singularities that are often hidden by recent sediments and allows target sampling and consequent detection of ecological particularities. RF-EM methods have traditionally been used to detect the presence of groundwater or the existence of subsurface contamination plumes. The great majority of such studies have been conducted on land and to a lesser extent on freshwater lakes but rarely in coastal waters. Previous research in Portugal has shown that despite the attenuation effect of salt water, very valuable information can be obtained with the use of electromagnetic methods, wherever resistivity contrasts exist. In the current case study, RF-EM surveys were carried out in the Estuary of the Guadiana River, in order to understand the importance of geological structures on the formation of the wetland and the influence of groundwater discharge on the existing ecosystem. Structures detected on land were also identified in the tidal channels. Freshwater fault springs were localized; their biota is characterized and the nutrients analysed. The results showed a clear increase in nitrate and silica concentration near the submarine springs, with impact on the planktonic communities, which is most evident in chlorophyll a. This is especially relevant during the end of summer and autumn when a potential limitation of these nutrients exists that can increase the occurrence of toxic blooms in the salt marshes and lower estuary. Copyright © 2012 John Wiley & Sons, Ltd.

The carbonate chemistry of seawater from the Ria Formosa lagoon was experimentally manipulated, by diffusing pure CO2, to attain two reduced pH levels, by − 0.3 and − 0.6 pH units, relative to unmanipulated seawater. After 84 days of exposure, no differences were detected in terms of growth (somatic or shell) or mortality of juvenile mussels Mytilus galloprovincialis. The naturally elevated total alkalinity of the seawater (≈ 3550 μmol kg− 1) prevented under-saturation of CaCO3, even under pCO2 values exceeding 4000 μatm, attenuating the detrimental effects on the carbonate supply-side. Even so, variations in shell weight showed that net calcification was reduced under elevated CO2 and reduced pH, although the magnitude and significance of this effect varied among size-classes. Most of the loss of shell material probably occurred as post-deposition dissolution in the internal aragonitic nacre layer. Our results show that, even when reared under extreme levels of CO2-induced acidification, juvenile M. galloprovincialis can continue to calcify and grow in this coastal lagoon environment. The complex responses of bivalves to ocean acidification suggest a large degree of interspecific and intraspecific variability in their sensitivity to this type of perturbation. Further research is needed to assess the generality of these patterns and to disentangle the relative contributions of acclimation to local variations in seawater chemistry and genetic adaptation.

Body condition in larval fishes is an important determinant of survival in the natural environment. However, few studies correlate body condition with behavioural traits critical for sur- vival, such as swimming performance. In the present study, we compared normally fed larvae of gilt- head seabream Sparus aurata Linnaeus, 1758, at various intervals post-hatch with larvae which were starved for 1 to 3 d (for Ucrit) or 2 d (for swimming endurance). Feeding treatment (fed and or unfed) had no effect on the relationship between Ucrit and larval size. However, in the endurance experi- ment, fed individuals swam twice as far as unfed larvae (19.7 km for fed larvae and 9.5 km for unfed larvae). The RNA/DNA ratio was higher in fed larvae in the Ucrit experiment, but significant effects were only detectable after a 3 d period of starvation. Fulton's condition factor was significantly higher in fed larvae in the endurance trial, which suggests that growth (in weight) of starved larvae was affected by long-term swimming. Taken together, these results suggest that for aging and orientation behaviours (activities in which critical speeds might be involved) are not affected by reduced feeding over a few days, but that sub-lethal effects of starvation may affect dispersal potential (for which endurance swimming is critical) and therefore compromise subsequent recruitment to the adult population.

This paper aims to set the record straight regarding the first observations of Corbicula fluminea (Muller, 1775) in the Guadiana River Basin. According to the available data, C. fluminea was first observed in 1988 and not in 2006 as suggested by Perez-Bote and Fernandez (2008). The first observations of C. fluminea in the Guadiana estuary were reported in 2000. In 2003, C. fluminea was already well established in the estuary and in many rivers and streams. C. fluminea is likely to expand its current biogeographic distribution in Portugal, since suitable lentic habitats for colonization will be crea ted by the implementation of the “National program of dams with high hydraulic potential”, which should be concluded by 2016.

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.

Temporal variation in the fatty acid (FA) composition of stomach contents of Iberian sardines was compared to the relative contribution to dietary carbon made by different prey types for fish from two areas off Portugal. The effect of the FA content of the diet on sardine muscle FA composition was also studied, aiming at (1) analysing if FA biomarkers can be used as a complementary technique for the study of sardine diet and (2) to relate spatial and temporal variations of prey FA content with sardine condition and reproduction. Significant spatial differences in the FA composition of sardine diet occurred with concentrations of n-3 polyunsaturated FA, namely eicosapentaenoic acid [EPA, 20:5n-3] and linolenic acid 18:3n-3, being significantly higher in the diet of sardines from the west coast, whilst the diet of sardines from the south coast was richer in monounsaturated fatty acids (MUFA), namely the carnivory biomarker oleic acid 18:1n-9. These results are in agreement with the higher contribution made by diatoms and dinoflagellates to the diet of sardines off the west coast. Spatial variation in sardine dietary FA was also detected in their muscle composition, specifically for EPA, and the eicosapentaenoic/docosahexaenoic acid and (n-3)/(n-6) ratios, which were higher in sardines from the west coast. No difference in FA composition was detected between sexes, and the seasonal variability in sardine total FA concentration was primarily related to the seasonality of spawning. Sardines accumulate high concentrations of FAs during the resting stage of reproduction when the feeding intensity is similar or lower to that observed during the spawning season. Additionally, sardines show a high selective retention of MUFA and polyunsaturated FA (PUFA) throughout the year except at the beginning of the spawning season, when these FAs are largely invested in the formation of the gonads. Therefore, temporal and regional differences of prey environments are strong enough to be reflected in fish body composition, namely on the accumulation of essential FAs, which can have a strong impact on reproduction success for this species.

Spatio-temporal variability of the diet of sardine Sardina pilchardus off Portugal was examined through analysis of the stomach contents of fish collected every 14 d from the west and south of Portugal during 2003/2004. Dietary composition of the modal sardine length class was assessed by determining the frequency of occurrence and carbon content of identified prey, and these 2 parameters were combined to estimate a modified index of relative importance of prey (mIRI). The most important prey for sardines were zooplankton, comprising crustacean eggs, copepods, decapods, cirripedes and fish eggs, dinoflagellates and diatoms (particularly the toxin-producer genus Pseudo-nitzschia), which together accounted for >90% of the estimated dietary carbon. Dietary seasonality was similar for both areas, except that the contribution of phytoplankton was higher for fish from the west Portuguese coast, where upwelling events are stronger and recurrent during spring and summer months. The predominance of prey

Clam-dredging results in the exposure of Spisula solida individuals not caught by the dredge. Subsequent survival depends on clam damage, reburial time, and the time needed by predators to reach the impacted area.We analyse these variables and discuss the importance of predation on exposed S. solida caused by dredge fishing. Sampling was performed in July 2000 off the southern coast of Portugal, at Vilamoura, a traditional S. solida sandy fishing ground.We compared the time needed for S. solida individuals to rebury themselves, relative to the abundance of potential predators. Bivalves collected by divers were placed on the seabed, and the times required for reburial were measured. These were compared with the times needed for reburial of the clams exposed by dredge impact. At each of three dredge tracks, we analysed the number of predators that entered three equal quadrats (0.0250 m2) per minute. These results were compared with a non-affected control area. Impact caused by the fishing dredge significantly increases the number of exposed S. solida clams ðp < 0:05Þ and the abundance of potential predatory species ðp < 0:05Þ. The brittle star Ophiura texturata was the most abundant and first species to reach the dredge track (less than 3 min after dredge impact). Other species reaching the dredge track were Pomatochistus spp. (6 min after impact), Diogenes pugilator, and Nassarius reticulatus (both 9 min after impact). Although predators reached the impacted area while S. solida bivalves were still exposed, our results suggest that predation on the non-buried clams in the dredge track is not a major factor for subsequent indirect mortality of S. solida.

12 páginas, 3 tablas.-- P. Range ... et al., The effects of seawater acidification caused by increasing concentrations of atmospheric carbon dioxide (CO2), combined with other climatic stressors, were studied on 3 coastal Mediterranean bivalve species: the mussel Mytilus galloprovincialis and the clams Chamelea gallina and Ruditapes decussatus. CO2 perturbation experiments produced contrasting responses on growth and calcification of juvenile shells, according to species and location. In the Northern Adriatic (Italy), long-term exposure to reduced pH severely damaged the shells of M. galloprovincialis and C. gallina and reduced growth for the latter species. Seawater in the Ria Formosa lagoon (Portugal) was consistently saturated in carbonates, which buffered the impacts on calcification and growth. After 80 days, no shell damage was observed in Portugal, but mussels in the acidified treatments were less calcified. Reduced clearance, ingestion and respiration rates and increased ammonia excretion were observed for R. decussatus under reduced pH. Clearance rates of juvenile mussels were significantly reduced by acidification in Italy, but not in Portugal. Both locations showed a consistent trend for increased ammonia excretion with decreasing pH, suggesting increased protein catabolism. Respiratory rates were generally not affected. Short-term factorial experiments done in Italy revealed that acidification caused alterations in immunological parameters of adult bivalves, particularly at temperature and salinity values far from the optimal for the species in the Mediterranean. Overall, our results showed large variations in the sensitivities of bivalves to climatic changes, among different species and between local populations of the same species. Expectations of impacts, mitigation and adaptation strategies have to consider such local variability., Funding was provided by the Foundation for Science and Technology (FCT) of Portugal (ERA- CIRCLE/0004/2007), the Regional Ministry of Innovation and Industry of the Galician Government, and the Italian Ministry for Environment, Land and Sea, in the framework of Circle ERA Net project (which is funded by the European Commission 6th Framework Programme). PR was also supported by a post-doctoral grant from FCT (SFRH/BPD/ 69959/2010)

Submitted by maria chicharo (mchichar@ualg.pt) on 2013-02-19T16:20:44Z No. of bitstreams: 1 rna dna in fish bivalve and crustacean 2007 m332p241.pdf: 81455 bytes, checksum: 1871db28eefe9a4d1644c905864bc0f5 (MD5) Approved for entry into archive by Merja Muzavor (mmuzavor@ualg.pt) on 2013-02-27T14:06:12Z (GMT) No. of bitstreams: 2 9565998912592254.zip: 75788 bytes, checksum: 19e43f6bcda0acff47fb6f4acdb9eb84 (MD5) rna dna in fish bivalve and crustacean 2007 m332p241.pdf: 81455 bytes, checksum: 1871db28eefe9a4d1644c905864bc0f5 (MD5) Made available in DSpace on 2013-02-27T14:06:12Z (GMT). No. of bitstreams: 2 9565998912592254.zip: 75788 bytes, checksum: 19e43f6bcda0acff47fb6f4acdb9eb84 (MD5) rna dna in fish bivalve and crustacean 2007 m332p241.pdf: 81455 bytes, checksum: 1871db28eefe9a4d1644c905864bc0f5 (MD5) Previous issue date: 2001

The influence of submarine groundwater discharges (SGD) on the dynamics ofcoastal ecosystems is receiving increasing scientific attention, although ourknowledge of this issue still remains insufficient. Understanding the ecologicalresponse of coastal ecosystems to SGD dynamics is important in order to eval-uate and predict changes in coastal communities. The aim of the present studywas to characterize the effect of groundwater discharge on subtidal soft-bottommacrofaunal assemblages in the south coast of Portugal (Algarve) at differenttimes of the year and under different discharge regimes. Sediment macrofaunawas sampled twice per season in spring and summer 2011 in two locations:one under influence of SGD (Olhos de Agua) and one not under that influence(Arrifes). The results showed that differences in community structure betweenlocations occurred mainly during spring, when the magnitude of groundwaterdischarge was higher. Several individual taxa were strongly associated with theSGD, particularly during spring: the polychaete families Magelonidae andOweniidae; the isopod Cyathura carinata;andthebivalvesTellimya ferruginosaand Tellina fabula. Some of these taxa are already considered indicators of SGD,whereas others merit further investigation. The average similarity among sam-ples was consistently larger in the location with SGD and the average similaritybetween the two locations was generally higher during spring, indicating thatSGD promote stability in macrobenthic communities across time and space.SGD were also associated with higher values of Chlorophyll a (Chl a), fine sed-iments and total abundance of organisms (particularly suspension feeders).This suggests that differences between locations are associated with SGD andmediated by nutrient fluxes and sediment transport, or their interaction.IntroductionSubmarine groundwater discharges (SGD) may representan additional source of freshwater to the coastal zonesince they are a widespread natural phenomenon that canoccur whenever an aquifer is hydraulically connected tothe coastal zone by permeable sediments and the head ofthe aquifer is above sea level (Johannes 1980). Alreadycalled ‘subterranean estuaries’ (Moore 1999), SGD canaccount for as much as 10% of the total freshwater inputto the coastal zone, with seepage areas acting as zones ofmixing of fresh and saltwater (Burnett et al. 2003). Therole of SGD in modulating salinity and as a supply ofsediments chemical compounds (e.g. nutrients, carbonand pollutants) into coastal areas is already well docu-mented (e.g. Johannes 1980; D’Elia et al. 1981; Valiela

There are numerous studies dealing with larvae of Small Pelagic Fish (SPF), but only a few have actually addressed advanced larval phases. Temperate coastal lagoons are particularly understudied, due to the absence of standard method to capture advanced larval fish in these near shore shallow habitats. Accordingly, this study aims to describe abundances, nutritional condition and in situ growth of postflexion (SPF) from the Ria Formosa, a tidal coastal lagoon in southern Portugal. The nutritional condition and in situ growth were determined through cohort analysis and standardized RNA:DNA ratio (sRD), complemented with feeding incidence (gut content) and fatty acids (FAs, trophic biomarkers) of postflexion larvae sampled sequentially with light traps, from spring 2005 to summer 2006. Simultaneously, environmental parameters such as water temperature, salinity, dissolved oxygen and chlorophyll a were measured. Post-larvae of SPF were captured through the year in important numbers. The dominant species were Sardina pilchardus (50.7%), Engraulis encrasicolus and Atherina presbyter (11.4%). These results are distinct from those based on adult/juvenile surveys or early planktonic phases in the Ria Formosa where clupeiformes were occasionally reported. Sardines were captured mainly in winter, spring and early summer and anchovies mainly during summer and autumn. Sand smelt, a resident species, was present throughout the year. In the early summer, the three species were present and during this period some diet overlapping occurred, the feeding incidence of the clupeiformes was very low, but atherinids always exhibited full guts reflecting the different gut morphology or indicating different lifecycle strategies. The bulk of the diet was mollusks, crustaceans and appendicularians, for sand smelts, sardines and anchovies, respectively. The results of FA analyses showed some contribution of phytoplankton to SPF in the area. All SPF exhibited higher condition (sRD) and growth rates in summer, which are explained by the adequate temperature and higher planktonic productivity. This is especially relevant because the successful development of postflexion larvae in these nursery areas largely determines the successful recruitment to adult fish populations. info:eu-repo/semantics/publishedVersion

Gaining reliable estimates of how long fish early life stages can survive without feeding and how starvation rate and time until death are influenced by body size, temperature and species is critical to understanding processes controlling mortality in the sea. The present study is an across-species analysis of starvation-induced changes in biochemical condition in early life stages of nine marine and freshwater fishes. Data were compiled on changes in body size (dry weight, DW) and biochemical condition (standardized RNA–DNA ratio, sRD) throughout the course of starvation of yolk-sac and feeding larvae and juveniles in the laboratory. In all cases, the mean biochemical condition of groups decreased exponentially with starvation time, regardless of initial condition and endogenous yolk reserves. A starvation rate for individuals was estimated from discrete 75th percentiles of sampled populations versus time (degree-days, Dd). The 10th percentile of sRD successfully approximated the lowest, life-stage-specific biochemical condition (the edge of death). Temperature could explain 59% of the variability in time to death whereas DW had no effect. Species and life-stage-specific differences in starvation parameters suggest selective adaptation to food deprivation. Previously published, interspecific functions predicting the relationship between growth rate and sRD in feeding fish larvae do not apply to individuals experiencing prolonged food deprivation. Starvation rate, edge of death, and time to death are viable proxies for the physiological processes under food deprivation of individual fish pre-recruits in the laboratory and provide useful metrics for research on the role of starvation in the sea. Highlights ► Biochemical condition (RNA–DNA ratio) decreases exponentially during starvation. ► Starvation parameters of individuals can be derived from data collected on groups. ► Physiological rates of starvation compare well across a broad range of temperatures. ► Species and life stages specific starvation parameters indicate selective adaptation.

The impoundment of rivers by large dams is the biggest direct anthropogenic impact on the hydrological cycle. However, dams can help solving eutrophication in estuaries by controlling flow pulses, which in turn might enhance the advection of fish larval stages from their spawning and nursery areas. Thus, this work aimed to merge data on the abundance of anchovy eggs with MOHID hydrodynamic model for the Guadiana estuary, allowing dam/basin managers to set river discharge scenarios that might mitigate/prevent eutrophication, without compromising the presence of fish larval stages inside the estuary. Data on anchovy larval stages were assessed in the Guadiana estuary and adjacent coast and three simulation setups were developed. In Simulation A, anchovy eggs abundance was merged in the hydrodynamic model to compare the outputs with data on the abundance, distribution and development stage of anchovy eggs and larvae. In Simulation B, lagrangian particles were incorporated in the model to determine the percentage of particles released from the upper, middle and lower estuary that remain in the estuary along 10 days, in two tidal situations and in seven river discharge scenarios. In Simulation C, the abundance of anchovy eggs was merged in the model to select the discharge scenario(s) that do not compromise the presence of anchovy larval stages in the estuary. Results confirmed the spawning and nursery areas of anchovy and showed that scenarios B (Qmax = 20 m3 s−1) and C (Qmax = 50 m3 s−1) should be applied during neap tides. The choice between scenarios depends on the degree of eutrophication, the effectiveness of an inexistent monitoring program and on plankton response experiments to flushing and increased nutrient loading. This work produced an easy-to-use management tool for Guadiana managers, serving as an example to other estuarine sites around the world. Ultimately, this work suggests that river flow management must be guided by robust ecological studies, under an adequate sociological framework and adopting sustainable economic principles to maintain and improve the ecosystem services. Copyright © 2010 John Wiley & Sons, Ltd.

We investigated the effects of ocean acidification on juvenile clams Ruditapes decussatus (average shell length 10.24 mm) in a controlled CO2 perturbation experiment. The carbonate chemistry of seawater was manipulated by diffusing pure CO2, to attain two reduced pH levels (by −0.4 and −0.7 pH units), which were compared to unmanipulated seawater. After 75 days we found no differences among pH treatments in terms of net calcification, size or weight of the clams. The naturally elevated total alkalinity of local seawater probably contributed to buffer the effects of increased pCO2 and reduced pH. Marine organisms may, therefore, show diverse responses to ocean acidification at local scales, particularly in coastal, estuarine and transitional waters, where the physical–chemical characteristics of seawater are most variable. Mortality was significantly reduced in the acidified treatments. This trend was probably related to the occurrence of spontaneous spawning events in the control and intermediate acidification treatments. Spawning, which was unexpected due to the small size of the clams, was not observed for the pH −0.7 treatment, suggesting that the increased survival under acidified conditions may have been associated with a delay in the reproductive cycle of the clams. Future research about the impacts of ocean acidification on marine biodiversity should be extended to other types of biological and ecological processes, apart from biological calcification.

This study aimed to determine whether and how the disruption of river flow, during the filling of the Alqueva dam, influenced the variability of abiotic and biotic factors in the Guadiana estuary, particularly the abundance and distribution of anchovy eggs. River inflow was found to be the most important factor in determining abiotic and biotic variability in the Guadiana estuary. Seasonal patterns were obscured by long periods of low inflow (mid April to early December 2002), which caused marked changes in the estuary. The estuarine turbidity maximum zone was displaced towards the upper estuary, to at least 38 km from the river mouth, 8 to 16 km upstream from previous records. The dynamics of nutrient stoichiometry was also affected. In the upper and middle estuary, P was more potential limiting than N and potential Si limitation was only frequent on the coast, with direct and/or indirect influence in changing phytoplankton dynamics and composition. Previously, the upper estuary alternated between potential P limitation during winter, Si limitation during spring and mid summer and N limitation during mid summer and autumn. The flooding of vast areas in the catchment of the dam probably caused the increase of DSi concentrations, as well as maximal N and P loadings. The abundance of larval stages of anchovy decreased, putatively because estuarine productivity has also decreased. In April 2002 there was an uncontrolled discharge from the Alqueva dam, which reduced the abundance of anchovy eggs by 99.99%. It is suggested that dam managers should mimic, as much as possible, the natural river flow, in order to minimize the impact on downstream ecosystems. Management efforts should not be restricted to the areas upstream of the dam, but should also encompass the estuary and adjacent coastal area.

We compared the fatty acid (FA) composition of the muscle and gonads of female Iberian sardines with hydrated oocytes collected during the 2002/03 spawning season off southern Portugal (November and February) and off western Portugal (February). Sardine condition and total FA concentration in the muscle decreased between the two sampling dates, while the gonadosomatic index was similar between samples. Total monounsaturated FA concentrations in sardine gonads were different for the three samples while saturated and polyunsaturated FA concentrations were similar. Significant linear relations were found between FA concentrations in female muscle and oocytes, including eicosapentaenoic acid (EPA; 20:5 n − 3) and arachidonic acid (AA; 20:4 n − 6), both being essential for normal larval development. The concentration of docosahexaenoic acid (DHA; 22:6 n − 3) in oocytes was independent on muscle concentration, probably resulting from its selective transfer to the oocytes. The EPA/DHA ratio was highly conserved in sardine tissues, while DHA/AA and EPA/AA ratios varied significantly between samples. These results indicate that the FA content of eggs produced by sardines varies throughout the spawning season, egg FA concentrations decreasing as females lose condition, and FA composition also shows spatial variability. Both types of variability may have a significant impact on egg quality, particularly on the amount of reserves available to larvae affecting their resistance to starvation, and the appropriate FA composition required for normal growth.

Submitted by maria chicharo (mchichar@ualg.pt) on 2013-02-19T15:30:50Z No. of bitstreams: 1 article FISH RES CHRONIC EFFECTS NUCLEIC ACID AND LIPIDS.pdf: 118928 bytes, checksum: 77a0a415f849d1fddb4fbdc1e8702a86 (MD5) Approved for entry into archive by Merja Muzavor (mmuzavor@ualg.pt) on 2013-02-26T15:54:29Z (GMT) No. of bitstreams: 2 9565998912592254.zip: 85507 bytes, checksum: 2e144f9f1ec4b29f71012a48081e13f5 (MD5) article FISH RES CHRONIC EFFECTS NUCLEIC ACID AND LIPIDS.pdf: 118928 bytes, checksum: 77a0a415f849d1fddb4fbdc1e8702a86 (MD5) Made available in DSpace on 2013-02-26T15:54:29Z (GMT). No. of bitstreams: 2 9565998912592254.zip: 85507 bytes, checksum: 2e144f9f1ec4b29f71012a48081e13f5 (MD5) article FISH RES CHRONIC EFFECTS NUCLEIC ACID AND LIPIDS.pdf: 118928 bytes, checksum: 77a0a415f849d1fddb4fbdc1e8702a86 (MD5) Previous issue date: 2003

Submitted by maria chicharo (mchichar@ualg.pt) on 2013-02-19T16:28:53Z No. of bitstreams: 1 COMPARING RNADNA TECHNIQUES GOBID JEMBE 245 2000.pdf: 392493 bytes, checksum: 5554b72fba1413bc2fbd6950af186926 (MD5) Approved for entry into archive by Merja Muzavor (mmuzavor@ualg.pt) on 2013-02-21T15:29:20Z (GMT) No. of bitstreams: 2 9565998912592254.zip: 291150 bytes, checksum: d58e0e3fe91b28524be6780d4573f1a4 (MD5) COMPARING RNADNA TECHNIQUES GOBID JEMBE 245 2000.pdf: 392493 bytes, checksum: 5554b72fba1413bc2fbd6950af186926 (MD5) Made available in DSpace on 2013-02-21T15:29:20Z (GMT). No. of bitstreams: 2 9565998912592254.zip: 291150 bytes, checksum: d58e0e3fe91b28524be6780d4573f1a4 (MD5) COMPARING RNADNA TECHNIQUES GOBID JEMBE 245 2000.pdf: 392493 bytes, checksum: 5554b72fba1413bc2fbd6950af186926 (MD5) Previous issue date: 2000

The aim of this study was to analyse the general larval condition, to determine the lncidence of starvation and to investigate the effect of time of day on RNA/DNA ratios among field-caught Sardina pilchardus (L.) larvae. The larvae were collected during 4 research cruises off northern Spain, during March, April, May and June 1992. A highly sensitive fluorometric method for nucleic acid quantification was applied to larvae of S. pilchardus. The means of the RNA/DNA ratio were relat~vely high, so the larvae collected off northern Spain were generally in good condition. Low percentages of starving larvae (RNA/DNA ratio less than 1.3), ranging from 0 to 3.23%, were found over the 4 mo. The RNA/DNA ratios were significantly correlated with zooplankton biomass. Larvae collected at night revealed higher RNA/DNA ratios compared to larvae caught during the day. This seems to indicate that there is some endogenous rhythm in the production of RNA. It would then follow that, if there are die1 changes in RNA concentrations, average RNA Indices can be unrepresentative if there IS any day/night bias in sampling.

Little attention has been given to the behavioural and physiological effects of dredging on clams. The response of the clam Spisula solida under stress imposed by dredging activity is analysed in terms of reburial time and two acute indices: AEC (adenylic energetic charge) and ATP per milligram dry weight. Stress on undersized (