Anthropogenic Modifications to Estuaries Facilitate the Invasion of Non-Native Species

ew observations of non-indigenous species (NIS) in coastal waters, such as the Gulf of Cadiz (Spain) have increased since 1980 and more or less exponentially in the last five years. Ballast water has become the most significant pathway for unintentional introductions of NIS into marine ecosystems. For example, the marine larvae of crustacean decapods that inhabit the water column could be transported in ballast water. Although elevated concentrations of metals are toxic to many marine organisms, some of them have evolved effective detoxification, or avoidance mechanisms making it possible to consider they have a superior ability to withstand exposures to these toxicants. In this text, we try to reinforce the hypothesis that anthropogenic modifications (such as chemical alterations and modified environments) benefit NIS with broad environmental tolerances. Taking these risks into account, a reinforcement of efficient Ballast Water Management Systems to respond to today's challenging environmental conditions is discussed.This essay was developed in the framework of the InvBlue project (PID2019105978RA-I00) from the Spanish "Ministerio de Economia y Competitividad (MINECO), Plan Nacional I + D", and within the 2014-2020 ERDF Operational Programme and Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia (Spain). Project Ref.: FEDER-UCA18 -108023. We thank Jon Nesbit for the English revision. We are also grateful to two anonymous referees for their critiques and suggestions that improved the manuscript

Scavenging behavior by Phyllonotus oculatus (Gastropoda: Muricidae) in a South Atlantic reef

Scavengers play a key role in nutrient cycling and in the energy transfer between the terrestrial-aquatic interface (Beasley et al. 2012). Obligatory scavengers feed exclusively on carrion, while some predator species act opportunistically as facultative scavengers when carrion is available (Morton 2006; Moleón and Sánchez-Zapata 2015). Species of the gastropod family Muricidae, such as Ergalatax contracta (Reeve, 1846), display the opportunistic habit of scavenging other predators’ leftovers on subtidal sands (Morton 2006). Muricidae is one of the largest families of carnivorous snails, utilizing a specialized shell-drilling ability to assess their prey (Dietl and Herbert 2005)

Mitogenome Phylogenetics in the Genus Palaemon (Crustacea: Decapoda) Sheds Light on Species Crypticism in the Rockpool Shrimp P. Elegans

[Abstract] The genus Palaemon comprises worldwide marine and freshwater shrimps and prawns, and some of them are ecologically or commercially important species. Palaemon is not currently a monophyletic group, so phylogenetics and systematics are constantly changing. Species crypticism has been pointed out in several Palaemon species, being the clearest evidence in the European rockpool shrimp P. elegans. Here we sequenced and described seven European Palaemon mitochondrial genomes. The mitochondrial protein-coding genes were used, along with those of three other Palaemon species, to perform mitogenome phylogenetic analyses to clarify the evolutionary relationships within the genus, and particularly to shed light on the cryptic species found within P. elegans. The Messinian Salinity Crisis (5.3-5.9 Ma, late Miocene) was proposed to be the origin of this cryptic species and it was used as aged constraint for calibration analysis. We provide the largest and the first time-calibrated mitogenome phylogeny of the genus Palaemon and mitogenome substitution rate was estimated (1.59% per million years) in Decapoda for the first time. Our results highlighted the need for future systematics changes in Palaemon and crypticism in P. elegans was confirmed. Mitochondrial genome and cox1 (1.41%) substitution rate estimates matched those published elsewhere, arguing that the Messinian Salinity Crisis was a plausible event driving the split between P. elegans and its cryptic species. Molecular dating suggested that Pleistocene glaciations were likely involved in the differentiation between the Atlantic and Mediterranean populations of P. elegans. On the contrary, the divergence between the Atlantic and Mediterranean populations of the common littoral shrimp P. serratus was greater and dated to be much older (4.5-12.3 Ma, Plio-Miocene), so we considered that they could represent two separated species. Therefore, species crypticism in the genus Palaemon seems to be a common phenomenon.Ministerio de Economía y Competitividad; CTM2014-53838-RXunta de Galicia; ED431C 2018/57This work was funded by a CTM2014-53838-R grant from the Spanish Government (Ministerio de Economía y Competitividad) and by a ED431C 2018/S7 grant from Xunta de Galici

Sea Cucumber (Holothuria arguinensis) as a Shelter for Juvenile Fish (Diplodus bellottii) in the Gulf of Cadiz (Southwestern Spain)

During a diving survey on soft-bottom habitats in the Gulf of Cadiz (Southwestern Spain), the use of the sea cucumber Holothuria arguinensis (Echinodermata, Holothuriidae) as a shelter by juvenile Senegal's sea bream Diplodus bellottii (Chordata: Sparidae) was observed. Eight juvenile sea bream D. bellottii were videoed sheltering under the sea cucumber's body. This observation highlights the importance of sea cucumbers as a shelter for juvenile fish, providing a microhabitat to take refuge from predators. This is the first report of juvenile sea bream sheltered by a sea cucumber

Trends in the species composition at the southernmost estuary of the Atlantic coast of Europe.

Climate change may enhance the establishment of introduced species, as well as the poleward shift in distribution of numerous species over decades. Long-term research and monitoring of an ecosystem at the southernmost point of the Atlantic coast of Europe should be an important priority in order to detect and understand trends in species composition and the related environmental changes. The Guadalquivir estuary (South Spain) is more likely to suffer the exacerbated effects of climate change due to its location in the Mediterranean-climate zone. The long-term data set between 1997 and 2015 in this estuary has allowed us to analyse the variability of the natural and anthropogenic stressors, especially in some dry years and how records of new species have been stabilised as a consequence of expanded connectivity (shipping) and “African Creep”. The mean interannual dissimilarity of the estuarine fauna (Bray–Curtis dissimilarity index) has showed important differences throughout the years, and the species that most contributed to these differences were the exotic species capable of completing their life cycles. Their average annual density has shown a continuous increase during the years of study in a period of expansion. This long-term monitoring of the estuarine community has allowed us to anticipate future events and ecological risk assessment in Europe due to climate change. Management implications are mainly related to the catching of exotic species to control their impact on native communities and reduce the shipping in this sort of ecosystem, which have been especially sensitive in the last 10 years

Width/length–weight relationships and condition factor of seven decapod crustaceans in a Brazilian tropical estuary

The analysis of body relationships and condition factors are useful tools in studies of marine populations, and they have been widely used in fishery research and management. In this study, width–weight (WWR) and length–weight (LWR) relationships and Fulton's condition factors were analyzed for six commercially important decapod crustacean species from the Paraguaçu River estuary (Todos os Santos Bay), eastern Brazil, namely Callinectes danae, C. exasperatus, C. marginatus, C. ornatus, Goniopsis cruentata and Ucides cordatus, and one non-indigenous species, Charybdis helleri. In total 5,704 individuals were measured and weighed during five years (2012–2017). The three allometric growth types for the crustacean species were observed, being most frequently the negative allometric growth. The analysis of covariance (ANCOVA) revealed significant differences between the sexes and climatic seasons in WWR/LWRs for the four species of the genus Callinectes, C. helleri, G. cruentata and U. cordatus, except for females and males of C. danae in WWR. The means for condition factor were generally higher for females than for males during the dry period, and in general, indicating good conditions for crustacean species. This study provided morpho-biometric parameters information will contribute stock management of traditional artisanal fisheries, and enable future comparative studies of populations of the same species.9 página

Environmental and anthropogenic drivers affect the abundance of anchovy and mysids in the Guadalquivir Estuary (SW Spain)

Natural drivers, acting at various spatio-temporal scales firstly determine the distribution and abundance of species. On top of this natural forcing we usually find anthropogenic effects. Disentangling the relative influence of these two sources of variability has always been a challenge in ecology, and particularly in fisheries science. The Guadalquivir Estuary (SW Spain) serves as nursery ground for several commercial species in the Gulf of Cadiz. This study aims at quantifying the relative influence of biological (predator-prey effects), environmental (e.g. temperature, winds) and anthropogenic (dam discharges) effects on this nursery function with the focus on an important species, anchovy. We used data from a monitoring programme consisting of monthly records since 1997 at two sites: Tarfia (32 km) and Bonanza (8 km) (distance from the river mouth). Nonparametric models (GAM) were fit to the data to estimate the partial effects of the various covariates. We found positive and linear effects of temperature and mysids on anchovy abundance in both stations, while turbidity, winds and freshwater input had a negative effect, reducing fish abundance. A dam, 110 km upstream from the Guadalquivir mouth regulates freshwater discharges, directly influencing the estuarine habitat quality and extent, as captured by our models. In order to separate the anthropogenic effects from natural variability we further ran the models on a number of scenarios combining a range of dam discharges and environmental conditions. Water management stands out as a key node where potentially conflicting interests (irrigators, electric power, shipping, aquaculture, fisheries) converge. By focussing on the consequences that the effects of these activities ultimately have on the anchovy fishery, through this nursery function, our study aims to contribute to the process of making the ecosystem approach operational in the Gulf of Cadiz

The nursery role of the Guadalquivir estuary for marine fish. A long-term ecological research

Trabajo presentado en el 23rd Biennial CERF Conference (Grand challenges in coastal and Estuarine Science: securin our future), celebrado en Portland (Oregón, US) del 8 al 12 de noviembre de 2015.N

Feeding Habits of the Invasive Weakfish (Cynoscion regalis) in the Gulf of Cadiz

Weakfish (Cynoscion regalis) has been present in Iberian waters since at least 2011, when it was first recorded in the Guadalquivir estuary. Little is known about the preferences and feeding strategies of weakfish outside of its native range; therefore, in this work, we carried out a comprehensive study between March 2021 and September 2021 to elucidate these matters. In total, the stomach contents of 300 fish were examined. The fish were collected in spring and summer in the Gulf of Cadiz (Spain), with individuals caught ranging from 185 to 590 mm in total length. Due to the sampling period and size range of individuals, ontogenic and seasonal (spring–summer) variations in the diet were also explored. Overall, fish and crustaceans were the dominant groups consumed by weakfish. The European anchovy (Engraulis encrasicolus) and caramote prawn (Penaeus kerathurus) were the most abundant prey in each group. While no differences were found in the percentage of occurrence of fish in the non-empty stomachs analyzed in spring and summer (83%), a small increase was found in the percentage of occurrence of crustaceans from spring (20%) to summer (29%). In addition, the analysis of the results also suggested that weakfish of smaller sizes feed more on crustaceans, while bigger individuals feed mainly on fish. Our findings indicate that weakfish is a fully carnivorous species with a preference for fish. All this is in line with the diet and strategy that weakfish exhibits in its native area and with the first assessment made with the existing population in the Sado Estuary (Portugal). In recent years, due to the appearance of non-native species, there is increasing concern among local fishermen and the local authorities about the reduction in captures of certain species such as Penaeus kerathurus; therefore, this study could help researchers to understand the role of weakfish concerning this matter. The present study contributes to the ecological knowledge about this species in the Iberian Peninsula and the Gulf of Cadiz, helping the local authorities to establish, if needed, an appropriate management program to cope with this recently introduced species

Salinity tolerance as a factor controlling spatial patterns in composition and structure of zooplankton in the Guadalquivir estuary

Trabajo presentado en ECSA 56 (Coastal systems in transition: From a 'natural' to an 'anthropogenically-modified' state), celebrado en Bremen del 4 al 7 de septiembre de 2016.N