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- Spatial and temporal scales of environmental forcing of Acartia populations (Copepoda: Calanoida) in the Canal de Mira (Ria de Aveiro, PortugalPublication . Leandro, Sérgio Miguel; Tiselius, Peter; Queiroga, HenriqueZooplankton and hydrological data were collected from August 2000 and June 2002 at six stations distributed throughout Canal de Mira (Ria de Aveiro, Portugal). The abundance of Acartia clausi and Acartia tonsa adults and juveniles of Acartia spp. for each station and month were combined in a three-way data matrix, which was decomposed into three two-way matrices corresponding to different modes: biological, time, and space. Cluster analysis applied on the space mode revealed the existence of three different zones as a consequence of zooplankton composition. At each mode, principal component analysis showed strong seasonal variations in zones 1 and 2. A different spatial pattern was found between the periods November 2000–April 2001 and November 2001–April 2002, with the displacement of the highest abundance levels from the middle estuary to near the mouth. The congeneric populations were segregated in space: the A. clausi population was restricted to downstream stations (zone 1), whereas the A. tonsa population dominated the middle estuary. Significant correlations between hydrological parameters and copepod abundance were found to differ from zone to zone. The statistical methodology was a valuable tool to (i) discriminate spatial and seasonal distribution patterns, (ii) define estuarine sections based on the faunistic composition, and (iii) evaluate delayed effects of phytoplankton.
- Copepod production estimated by combining in situ data and specific temperature-dependent somatic growth modelsPublication . Leandro, Sérgio Miguel; Tiselius, Peter; Marques, Sónia Cotrim; Avelelas, Francisco; Correia, Catarina; Queiroga, HenriqueAlthough growth in adult copepods is frequently assumed to be similar to juvenile growth, some evidence have pointed out that under in situ conditions, it can be lower, with, as a consequence, underestimation of secondary production. In addition, under field conditions, juvenile growth in copepods is close to maximum rates estimated at food-saturated conditions. Based on previous assumptions, this study aimed to test the applicability of a new approach for copepod production estimate, derived from temperature-dependent growth models and in situ data, such as seawater temperature and copepod biomass. For this purpose, site-specific copepod juvenile growth models, defined for Acartia tonsa and A. clausi populations from a Southern European estuary (Canal de Mira, Ria de Aveiro, Portugal), were used and copepod biomass was taken fromzooplankton samples collected during 2 years at six sampling stations. By comparing the obtained results with published data, the feasibility of the approach for copepod secondary production estimates and its applicability in worldwide marine ecosystems was confirmed. Future studies should combine the estimates of adult and juvenile production in order to evaluate its relative contribution and to obtain a more precise estimate of secondary production.
- Predicting zooplankton response to environmental changes in a temperate estuarine ecosystemPublication . Marques, Sónia Cotrim; Azeiteiro, Ulisses Miranda; Leandro, Sérgio Miguel; Queiroga, Henrique; Primo, Ana Ligia; Martinho, Filipe; Viegas, Ivan; Pardal, Miguel ÂngeloA novel strategy that allows to predict the responses of zooplanktonic species to environmental conditions in an estuarine temperate ecosystem (Mondego estuary) is presented. It uses 12 indicator species from the zooplanktonic Mondego database (102 species) that are common members of the different habitats, characterized by their specific hydrological conditions. Indicator-species analysis (ISA) was used to define and describe which species were typical of each of the five sampling stations in a 4-year study (2003–2006). First, a canonical correspondence analysis (CCA) was carried out to objectively identify the species-habitat affinity based on the relationship between species, stations and environmental data. Response curves for each of the zooplanktonic species, generated by univariate logistic regression on each of the independent variables temperature and salinity, were generally in agreement with the descriptive statistics concerning the occurrence of those species in this particular estuarine ecosystem. Species-specific models that predict probability of occurrence relative to environmental parameters like salinity, water temperature, turbidity, chlorophyll a, total suspended solids and dissolved oxygen were then developed for the zooplanktonic species. The multiple logistic models used contained between 1 and 3 significant parameters and the percentage correctly predicted was moderate to high, ranging from 62 to 95%. The predictive accuracy of the model was assured by direct comparison of model predictions with the observed occurrence of species obtained in 2006 (validation) and from data collected in the early 2000s in another Portuguese estuary - Ria de Aveiro (Canal de Mira), a complex mesotidal shallow coastal lagoon. The regression logistic model here defined, correctly suggested that the distribution of zooplankton species was mainly dependent on salinity and water temperature. The logistic regression proved to be a useful approach for predicting the occurrence of species under varying environmental conditions at a local scale. Therefore, this model can be considered of reasonable application (and should be tested in other estuarine systems) due to its ability to predict the occurrence of individual zooplanktonic species associated with habitat changes.
- Harvest locations of goose barnacles can be successfully discriminated using trace elemental signaturesPublication . Albuquerque, Rui; Queiroga, Henrique; Swearer, Stephen E.; Calado, Ricardo; Leandro, Sérgio M.European Union regulations state that consumers must be rightfully informed about the provenance of fishery products to prevent fraudulent practices. However, mislabeling of the geographical origin is a common practice. It is therefore paramount to develop forensic methods that allow all players involved in the supply chain to accurately trace the origin of seafood. In this study, trace elemental signatures (TES) of the goose barnacle Pollicipes pollicipes, collected from ten sites along the Portuguese coast, were employed to discriminate individual’s origin. Barium (Ba), boron (B), cadmium (Cd), chromium (Cr), lithium (Li), magnesium (Mg), manganese (Mn), phosphorous (P), lead (Pb), strontium (Sr) and zinc (Zn) - were quantified using Inductively Coupled Plasma−Mass Spectrometry (ICP-MS). Significant differences were recorded among locations for all elements. A regularized discriminant analysis (RDA) revealed that 83% of all individuals were correctly assigned. This study shows TES can be a reliable tool to confirm the geographic origin of goose barnacles at fine spatial resolution. Although additional studies are required to ascertain the reliability of TES on cooked specimens and the temporal stability of the signature, the approach holds great promise for the management of goose barnacles fisheries, enforcement of conservation policies and assurance in accurate labeling.
- Spatial and temporal scales of environmental forcing of Acartia populations (Copepoda: Calanoida) in the Canal de Mira (Ria de Aveiro, Portugal)Publication . Leandro, Sérgio Miguel; Tiselius, Peter; Queiroga, HenriqueZooplankton and hydrological data were collected from August 2000 and June 2002 at six stations distributed throughout Canal de Mira (Ria de Aveiro, Portugal). The abundance of Acartia clausi and Acartia tonsa adults and juveniles of Acartia spp. for each station and month were combined in a three-way data matrix, which was decomposed into three two-way matrices corresponding to different modes: biological, time, and space. Cluster analysis applied on the space mode revealed the existence of three different zones as a consequence of zooplankton composition. At each mode, principal component analysis showed strong seasonal variations in zones 1 and 2. A different spatial pattern was found between the periods November 2000–April 2001 and November 2001–April 2002, with the displacement of the highest abundance levels from the middle estuary to near the mouth. The congeneric populations were segregated in space: the A. clausi population was restricted to downstream stations (zone 1), whereas the A. tonsa population dominated the middle estuary. Significant correlations between hydrological parameters and copepod abundance were found to differ from zone to zone. The statistical methodology was a valuable tool to (i) discriminate spatial and seasonal distribution patterns, (ii) define estuarine sections based on the faunistic composition, and (iii) evaluate delayed effects of phytoplankton.