Browsing by Author "Gamito, Sofia"
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- Benthic ecology of semi-natural coastal lagoons, in the Ria Formosa (Southern Portugal), Exposed to different water renewal regimesPublication . Gamito, SofiaSeveral studies in semi-natural coastal lagoons in the Ria Formosa lagoonal system have been carried out. These man-made water reservoirs behave as small lagoons with one opening to the tidal channels, which may be intermittent. Because of their size, these reservoirs are ideal sites for ecological studies. Water quality and macrobenthic fauna were analysed in five water reservoirs. All reservoirs received the same incoming water through a tidal channel, but they differed in water renewal regime. Multidimensional Scaling (MDS) and Discriminant Analysis were used to evaluate the similarity among sites, stations and sampling occasions. Different levels of taxonomic resolution (family, large taxonomic groups and phylum level) were also evaluated. The separation of sites and stations became unclear using high taxonomic levels. Results from the multivariate analyses suggest a slight differentiation of the stations according to sampling occasion but a clear differentiation of the several water reservoirs. Some of the lagoons studied with low water renewal rates showed strong environmental variations. They were characterised by low diversity indexes and abundance of small-sized organisms. Other lagoons, with high water renewal rates, showed low environmental variation and well diversified and structured benthic communities. The main environmental factor that seems to affect the benthic communities was the variation in salinity between neap and spring tides, which is related with the water renewal regime. Coastal lagoons offer a protected shallow habitat, which can be highly productive. Well structured communities, controlled by k-strategists, can develop and settle in leaky lagoons, that is, lagoons with wide entrance channels and tidal currents which guarantee a good water renewal. In these lagoons, biomass can accumulate in large organisms. In contrast, lagoons with a single narrow entrance, that may be closed for long periods, are characterised by persistent physical stress and are dominated by communities of small-sized r-strategists.
- Caution is needed when applying Margalef diversity indexPublication . Gamito, SofiaThe use of diversity indices has increased due to the necessity of testing different methodologies to develop the ecological status classification of water bodies within the water framework directive implementation. The Margalef diversity index is one of the indices applied within these aims. Several software packages calculate various diversity indices. However, these packages do not give any warning that for the Margalef index the data must be organized as absolute numbers and not as a density data matrix. In data expressed as number of individuals per square meter, if the sample size is lower than a square meter this index is sub estimated. With other diversity indices commonly used in ecological evaluation it is indifferent to use density data or absolute numbers since these indices only consider relative proportions in their calculus.
- Feeding diversity in macroinvertebrate communities: a contribution to estimate the ecological status in shallow watersPublication . Gamito, Sofia; Furtado, RamilaThe feeding diversity of subtidal samples of macroinvertebrates from Ria Formosa was estimated with Shannon Wiener information index and complementary evenness. The results were compared with other commonly used methodologies under the European water framework directive, such as diversity indices, AMBI and ITI. Assuming that in a healthy environment all feeding groups are present, and that no group clearly dominates, the feeding diversity is expected to be maximal and the evenness feeding diversity will be close to 1. In degraded environments some feeding groups might be absent or having low relative abundance, and generally with one or two groups dominating the community. In this way the evenness feeding diversity index would measure deviations from expected values due to a degradation of the environment. Although confirmation of this approach needs to be tested in other shallow waters, the results obtained show interesting features. To each of the 297 species belonging to the Ria Formosa data matrix a feeding group was assigned, among six groups: surface deposit feeders, sub surface deposit feeders, herbivores, suspension feeders and suspension/deposit feeders (species which have the two feeding modes depending on food availability). The carnivorous, parasites, omnivorous and scavengers were all grouped together, forming the sixth group. Most of the stations of Ria Formosa showed high feeding diversity, which could correspond to a good or high ecological status (ES) except at one location, that occasionally showed low feeding diversity. This poor condition was essentially due to low water renewal and extreme environmental variation of some parameters, such as salinity. At some locations an intermediate feeding diversity was observed mainly due to natural accumulation of organic matter. Other commonly used indices also point out to the same tendencies. We propose the evenness feeding diversity estimate approach as a practical and apparently robust method to estimate the ES of shallow waters, which can be used together with other common indicators. This approach has also the advantage of showing low sensibility to small samples and to low taxonomic identification effort.
- Feeding diversity index as complementary information in the assessment of ecological quality statusPublication . Gamito, Sofia; Patrício, Joana; Neto, João M.; Teixeira, Heliana; Marques, João CarlosThe feeding diversity of macroinvertebrates from the estuary of Mondego was estimated with Shannon–Wiener complementary evenness following the methodology presented in Gamito and Furtado (2009. Ecological Indicators, 9: 1009-1019). Results were compared with those from BAT (Benthic Assessment Tool; Teixeira et al., 2009. Marine Pollution Bulletin, 58: 1477-1786) applied to the same data set, obtained from sampling carried out in 14 estuarine subtidal stations in Spring of 1990, 1992, 1998, 2000 and 2002. The BAT is a multimetric methodology based on three indices, the Shannon-Wiener and Margalef diversity indices, applied in conjunction with AMBI (Marine Biotic Index). To determinate the feeding diversity, each invertebrate was assigned to a feeding group. Six trophic groups were considered: surface deposit feeders, subsurface deposit feeders, herbivores or grazers, suspension feeders and suspension/deposit feeders. The carnivorous, omnivorous and scavengers were all grouped together, forming the sixth group. The results obtained with both tools pointed out, in general, to the same tendencies. However, in few occasions the feeding diversity pointed out to a high or a bad ecological quality condition whereas the BAT indicated a moderate condition. Occasionally, in stations with average species richness, all individuals were assigned to only one to three 2 feeding groups, and the feeding diversity was low. Even if these taxa were included in the first two or three AMBI sensitive groups, with their presence indicating a possible good ecological condition, they all perform the same ecological function, for example, they are all omnivorous. In these cases the trophic functioning of the system is reduced and the lower trophic levels are missing, such as the suspension-feeders and the decomposers or deposit-feeders. On the contrary, a highly diverse trophic assemblage might be found, but composed of taxa assigned to AMBI ecological groups of species indifferent or tolerant to organic enrichment, and of second-order opportunistic species, indicating a moderate ecological condition, while the feeding diversity will be high. The feeding diversity is, therefore, useful as a complementary information index, measuring other aspects of the community organization, which are not required for ecological quality assessment by the WFD, and so not included in metrics such as BAT.
- Feeding habits of the gilthead seabream (Sparus aurata) from the Ria Formosa (southern Portugal) as compared to the black seabream (Spondyliosoma cantharus) and the annular seabream (Diplodus annularis)Publication . Pita, C.; Gamito, Sofia; Erzini, KarimThe feeding habits of Sparus aurata L., Diplodus annularis L. and Spondyliosoma cantharus L. in the Ria Formosa (southern Portugal) lagoon system were studied using three simple methods (frequency of occurrence, numeric percentage and percentage weight) and a composite index [index of relative importance (IRI)]. The Ivlev index was used to evaluate diet selectivity, while the Schoener overlap index was used to compare diets, and diet diversity was characterized by the Simpson index. The diets of the three species consist of a wide variety of food organisms, nevertheless S. aurata seems to be the most specialized. No significant dietary overlap was found, with S. aurata preferentially selecting gastropods and bivalves. while S. cantharus preferentially selected a wide variety of crustaceans and D. sargus a wider array, including crustaceans, gastropods and bivalves.
- Food availability and the feeding ecology of ichthyofauna of a Ria Formosa (South Portugal) water reservoirPublication . Gamito, Sofia; Pires, A.; Pita, C.; Erzini, KarimThe feeding habits of several fish species in a water reservoir of the Ria Formosa, Portugal, that has similar ecological characteristics to the outside tidal channels, were studied and compared with food availability. The gilthead seabream (Sparus aurata), the most abundant fish species, mainly selected gastropods and bivalves, although occasionally fish and small crustaceans such as tanaids, ostracods, and cumaceans were also selected. Polychaetes, although abundant in the environment, were not particularly selected by any of the fish species studied. The diets of all the species studied were characterized by a large variety of prey, allowing them to survive in environments of low diversity and poor stability, such as coastal lagoons. These fish are largely benthic feeders, essentially eating the epimacroinvertebrates and endomacroinvertebrates and, occasionally, fish. Diplodus vulgaris and Diplodus annularis preferentially selected gastropods and small crustaceans. Spondyliosoma cantharus generally preyed on crustaceans, including the highly mobile epifauna, the mysids, and decapods. Halobatrachus didactylus and Anguilla anguilla, had very diversified diets that included fish. Mullus barbatus were found to have selected all groups of crustaceans and also bivalves. Wrasses, gobies, and Diplodus sargus, all small-sized fish, singled out small crustaceans, gastropods, and bivalves. The Sparids were the least specialized predators, with broader niches than the other species. They preferentially selected molluscs, which were abundant in the environment. A large overlap of diets was observed and competition may be important when fish biomass is high.
- Integrated assessment of bioerosion, biocover and downwearing rates of carbonate rock shore platforms in southern PortugalPublication . Moura, Delminda; Gabriel, Selma; Gamito, Sofia; Santos, Rui; Zugasti, Estibaliz; Gomes, A.I.; Tavares, Ana Mafalda; Martins, Ana LuísaBioerosion on rocky shores has been frequently reported as an important mechanism in coastal evolution, with less attention focussed on determining the bioprotective role organisms may have in mediating coastal erosion. This work aims, for the first time, to provide an integrated assessment of both traversing microerosion meter (TMEM) downwearing rates and activity of intertidal organisms on two carbonate shore platforms in southern Portugal. Paired substations positioned on the same substrate but differing in biological cover (one with bare rock and the other with algal cover colonised between the first and final readings) were monitored for eighteen months using a TMEM. At each station, the volume of burrows produced by macro borers was measured. Downwearing rates were lower in the surfaces protected by algal turf except in the station that experienced the longest time of exposure to subaerial conditions. In contrast, TMEM downwearing rates were higher in the areas containing the higher volume of burrows. Both downwearing rates and burrow volumes were negatively correlated with the mechanical strength of the substrate as measured by Schmidt Hammer rebound.
- Integrated multi-trophic aquaculture systems: energy transfers and food web organization in coastal earthen pondsPublication . Gamito, Sofia; Quental-Ferreira, H; Parejo, A; Aubin, J; Christensen, V; Cunha, METhree Ecopath models were built to reproduce 3 experimental treatments carried out in earthen ponds located in Olhao, southern Portugal, to understand the energy transferred and the ecosystem state in integrated multi-trophic aquaculture (IMTA). These earthen ponds behave as simplified ecosystems or mesocosms, with well-defined borders, where the relationships between trophic groups can be described through ecosystem modeling. Different combinations of species were produced in these ponds, corresponding to the 3 treatments: (1) fish, oysters and macroalgae (FOM); (2) fish and oysters (FO); and (3) fish and macroalgae (FM). The managed species were meagre Argyrosomus regius, white seabream Diplodus sargus, flathead grey mullet Mugil cephalus, Japanese oyster Crassostrea gigas and sea lettuce Ultra spp. The results showed that the total amount of energy throughput was 15 to 17 times higher when compared with an equivalent naturalized system. The high biomass and low recycling indicated an immature system with low resilience and low stability that demands high rates of water renewal and aeration to maintain good water-quality levels for finfish production. The addition of oysters and macroalgae in the FOM treatment appeared to improve the water quality, since oysters controlled the excess of phytoplankton produced in the ponds by ingesting a fair amount of the phytoplankton, while the macroalgae helped in the absorption of excess nutrients and created a habitat for periphyton and associated macroinvertebrates. Some ecosystem attributes of the FOM ponds approached the values of the naturalized model, suggesting a possible path towards more sustainable aquaculture.
- Macroinvertebrates associated with macroalgae within integrated multi-trophic aquaculture (IMTA) in earthen ponds: potential for accessory productionPublication . Vieira, Rafael; Mateus, Miguel; Afonso, Carlos; Soares, Florbela; Pousão-Ferreira, Pedro; Gamito, SofiaThe present work aims to evaluate the macroinvertebrate community associated with macroalgae in earthen pond systems to better understand their potential in detritus recycling and as an accessory production. Sampling took place on the settling pond of an aquaculture research station, where macroalgae permanently occurred at high densities. The results suggest differentiation between seasons but not between sites within the settling pond. Seasonal variation was observable in terms of macroinvertebrate density, biomass, and diversity. Two non-indigenous species of invertebrates were found, the crustaceans Grandidierella japonica and Paracerceis sculpta Amphipods were the most abundant group, and their high nutritional value can be exploited. Detritus and the epiphyte layer are the main food items for the invertebrates, reinforcing the advantages of these organisms being present to enhance the recycling of excess detritus and to transfer organic matter to upper trophic levels. These species, naturally present in aquaculture facilities, can improve the water quality and increase the variability of food nutrients for reared species.
- Methodology for assessing the individual role of fish, oyster, phytoplankton and macroalgae in the ecology of integrated production in earthen pondsPublication . Cunha, M.E.; Quental-Ferreira, H.; Parejo, A.; Gamito, Sofia; Ribeiro, L.; Moreira, M.; Monteiro, I.; Soares, F.; Pousão-Ferreira, PedroProduction costs in extensive and semi-intensive fish culture in earthen ponds are often too high to offer sustainable economic activity due to the low productivity of these systems. The right combination of commercial finfish species with inorganic (primary producers) and organic extractive (bivalves) species in Integrated MultiTrophic Aquaculture (IMTA) create a balanced system with higher profitability and risk reduction. To achieve this, it is crucial to understand the role of each functional groups within the system what we did by comparing three different IMTA production three different IMTA production treatments with distinct combinations of trophic levels: •fish, filter feeders, phytoplankton and macroalgae,•fish, filter feeders and phytoplankton•fish, phytoplankton and macroalgae Each treatment was carried out in two similar ponds under semi-intensive conditions and flow through system, in a total of 6 earthen ponds of 500 m2 surface and depth of 1.5 m. Results showed that the presence of oysters in the ponds enhanced water quality by decreasing turbidity and by controlling phytoplankton which led to regulation of dissolved oxygen levels. The enhanced water quality in these systems lead to improved fish performance and higher biomass production contributing to greater profitability. The combination of fish, oyster, phytoplankton and macroalgae was particularly good providing much more fish supply compared with the other two treatments. •Oysters enhanced water quality in the ponds by decreasing turbidity and controlling phytoplankton which regulated the dissolved oxygen levels.•The enhanced water quality in systems with oysters improve fish performance resulting in higher biomass production and greater profitability.•The combination of fish, oyster, phytoplankton and macroalgae was particularly good providing much more fish supply compared with the other two treatments.