How can science contribute for the sustainable management of natural resource? : Praia da Vitória Bay and Guadiana Estuary, a comparative study

Tese de Doutoramento, Ciências do Ambiente (Ordenamento do Território), 5 de Abril de 2013, Universidade dos Açores.

Natural and anthropogenic factors controlling algae growth in the Ythan Estuary, Aberdeenshire

The Ythan Estuary in Aberdeenshire is a Site of Special Scientific Interest due to the numerous protected species which incorporate it into their ecosystem. In recent years algae growth in the estuary has been seen to increase, causing concern over the integrity of the estuary as a habitat for wildlife. By examining sediment, river flow, nutrient levels and temperature it is possible to identify the driving factors behind this increased algal growth. Using data gathered in the field as well as historical climate data the contribution of each of these factors to algae growth can be determined.

Changes in the annual harmful algal blooms of Alexandrium minutum : effects of environmental conditions and drainage basin inputs in the Rance estuary (Brittany, France)

Time series of physico-chemical data and concentrations (cell L-1) of the toxic dinoflagellate Alexandrium minutum collected in the Rance macrotidal estuary (Brittany, France) were analyzed to understand the physico-chemical processes of the estuary and their relation to changes in bloom development from 1996 to 2009. The construction of the tidal power plant in the north and the presence of a lock in the south have greatly altered hydrodynamics, blocking the zone of maximum turbidity upstream, in the narrowest part of the estuary. Alexandrium minutum occurs in the middle part of the estuary. Most physical and chemical parameters of the Rance estuary are similar to those observed elsewhere in Brittany with water temperatures between 15–18 °C, slightly lowered salinities (31.8–33.1 PSU), low river flow rates upstream and significant solar radiation (8 h day-1). A notable exception is phosphate input from the drainage basin which seems to limit bloom development: in recent years, bloom decline can be significantly correlated with the decrease in phosphate input. On the other hand, the chemical processes occurring in the freshwater-saltwater interface do not seem to have an influence on these occurrences. The other hypotheses for bloom declines are discussed, including the prevalence of parasitism, but remain to be verified in further studies.

Between the Atlantic and the Mediterranean : the late bronze age around the Tagus estuary (Portugal) : economic, social and cultural aspects

This paper deals with the importance, quantity and diversity of Late Bronze Age sites known around the Tagus estuary. The material culture points out to the existence of cultural stimuli from very different origins: from the Iberian Peninsula inner, the North Atlantic and the Mediterranean basin, related to the social organization and the economy of the populations that inhabited this region between the XIII century BC and the IX century BC, according to the available radiocarbon data. These populations interacted with the first Phoenicians that arrived to the region at the end of this period, after episodic relations of trading with their antecedents, from Central Mediterranean region.

[Location map of Kidwell's Meadows in the Potomac River estuary, Washington D.C.].

Covers marsh which later became part of West Potomac Park.

Longitudinal distribution and lateral pattern of megalopal settlement and juvenile recruitment of Carcinus maenas (L.) (Brachyura, Portunidae) in the Mira River Estuary, Portugal

Settlement is a critical process in the life history of crabs, and thus affecting the abundance, distribution and structure of estuarine communities. The spatial pattern of settlement of megalopae of the shore crab Carcinus maenas along a longitudinal estuarine gradient (Mira River Estuary, Portugal) was examined, as well as its effects on the juvenile population. To measure megalopal settlement, four replicate collectors were deployed in six equally spaced stations along the estuarine axis. Juveniles were collected on the same locations with a quadrat randomly deployed on the substrate. To assess fine-scale megalopal settlement within a curved region of the estuary, replicate collectors were deployed on both margins along Moinho da Asneira curve. Megalopae settled differently along the six longitudinal points, with a tendency to attenuate their settlement upstream. Within the curved region, megalopae preferentially settled on the left margin collectors, probably due to the weaker velocity speeds felt on this margin. Concerning the overall juvenile density, there were significant differences among the stations distributed along the estuary, but they did no reflect a longitudinal dispersion attenuation pattern. Size-frequency distribution of the juvenile population showed that the average size is higher on the left margin. Recruits (carapace length between 1.0 mm and 3.4 mm) were more abundant on the upstream stations. Density of early juveniles (3.4 mm-6.5 mm) and juveniles (6.5 mm-10 mm) was more stable throughout the estuary axis than that of recruits. This distribution pattern may result from tidal excursion processes or mechanisms to avoid biotic interactions, such as predation and competition. (c) 2006 Elsevier Ltd. All rights reserved.

Evaluation of solid residues removed from a mangrove swamp in the Sao Vicente Estuary, SP, Brazil

Mangrove swamps are found in estuaries along the coastal plains of tropical regions and have be subjected to heavy occupation and use pressure due to their privileged locations and abundance of biological resources. The present work evaluated the ecological characteristics and solid wastes accumulated in eight areas along the Santos - Sao Vicente Estuary Complex. The superficially deposited residues at each sampling site were collected and subsequently washed, drained, counted, weighed and separated into classes according to their composition and predominant use. The predominant litter type in terms of density was plastic (62.81%) and, by weight, wood (55.53%). The greatest deposition of residues was associated with areas that were less inclined and that had low plant density levels, indicating that the presence of obstacles was not critical for retaining floating residues in mangrove areas. The presence of the most frequently encountered types of solid waste residues could be explained by local activities. (C) 2010 Elsevier Ltd. All rights reserved.

Feeding ecology and trophic relationships of fish species in the lower Guadiana River Estuary and Castro Marim e Vila Real de Santo Antonio Salt Marsh

In this study we analyze the feeding ecology and trophic relationships of some of the main fish species (Soleidae, Moronidae, Mullidae, Sparidae, Mugilidae, and Batrachoididae) of the lower Estuary of the Guadiana River and the Castro Marim e Vila Real de Santo Antonio Salt Marsh. We examined the stomachs of 1415 fish caught monthly between September 2000 and August 2001. Feeding indices and coefficients were determined and used along with the results of multivariate analysis to develop diagrams of trophic interactions (food webs). Results show that these species are largely opportunistic predators. The most important prey items are amphipods, gobies (Gobiidae), shrimps (Palaemon serratus and Crangon crangon), and polychaete worms. The lower Estuary and associated salt marshes are important nurseries and feeding grounds for the species studied. In this area, it is therefore important to monitor the effects of changes in river runoff, nutrient input, and temperature that result from construction of the Alqueva Dam upstream. (c) 2006 Elsevier Ltd. All rights reserved.

Weight-length relationships for 54 species of the Arade estuary, southern Portugal

P>Weight-length relationships (WLRs) are presented for 54 species sampled by several types of fishing gear between February 2004 and May 2007, in the Arade estuary (southern Portugal). WLRs for six species are presented for the first time.

Diets of the sole Solea vulgaris Quensel, 1806 and Solea senegalensis Kaup, 1858 in the lower estuary of the Guadiana River (Algarve, southern Portugal): Preliminary results

The feeding habits of two major species of sole, the common sole Solea vulgaris Quensel, 1806 and the Senegalese sole Solea senegalensis Kaup, 1858 were studied in the lower estuary of the Guadiana River (Algarve, southern Portugal). An evaluation of the number, weight, and feeding coefficient of prey types showed that S. vulgaris feed on a limited variety of prey (only Polychaeta and Tanaidacea) and present low-intensity feeding activity, with small differences in diet between seasons. S. senegalensis also have a low-diversity diet (with only one more taxa, Amphipoda), but exhibit more intense feeding activity which varies seasonally, although with little seasonal variation in the relative importance of the main preys. The diet composition of these two species suggests feeding specialization.

Benthic nematodes biodiversity patterns along the gradient of the Tagus estuary (Western Coast of Portugal): Link with abundances distribution pattern of the nonindigenous bivalve Ruditapes philippinarum

The non-indigenous bivalve Ruditapes philippinarum is native to the western Pacific Ocean and it has been one of the most widely introduced species for aquaculture purposes in Europe. In Portugal its presence is known in several estuaries for more than two decades and its populations have increased greatly along the last years1. Currently it’s one of the dominant benthic species in some areas of the Tagus estuary (264,1±470,8 ind./30s tow). Studies on the impacts of invasive bivalves on meiofaunal communities are scarce and restricted to the harvesting effect. Meiofauna of the Tagus estuary is poorly known and possible impacts of the introduction of R. philippinarum were never assessed.