Population Genetic Structure of Neotropical Mangrove Species on the Colombian Pacific Coast: Avicennia germinans (Avicenniaceae)1

We investigated the genetic variation of Avicennia germinans using 172 AFLP (Amplified Fragment Length Polymorphism) bands of 45 plants from four localities on the Colombian Pacific coast: 11 from Virudó (Chocó), 10 from La Plata (Valle), 12 from Tumaco (Nariño), and 12 from Chontal (Nariño). AFLP variation among localities (16.2%) was highly significant (AMOVA; P < 0.0001). All the analyses showed that Tumaco was the most genetically distinct locality of the four under study. The other three localities, La Plata, Virudó, and Chontal, apparently form a large single subpopulation with high‐to‐moderate gene flow among localities. We also found the genetic diversity of A. germinans on the Colombian Pacific coast (H_E= 0.251) higher than that estimated by others over the broad geographic range of A. germinans. All these results together show that mangroves on the Colombian Pacific coast deserve a strong investigative effort to improve our ecological, evolutionary, and biogeographic knowledge of this important tropical forest type.     

Habitat use and nursery evaluation for the longnose stingray Hypanus guttatus (Bloch & Schneider, 1801) using vertebral microchemistry

Here, we use vertebral microchemistry to investigate the habitat use patterns of the longnose stingray Hypanus guttatus in the northern and northeastern regions of Brazil, and to evaluate the existence of potential nurseries of the species. Samples were collected in Maranhão, Rio Grande do Norte and Pernambuco states between 2008 and 2019. Trace element concentrations of Ba:Ca, Mg:Ca, Mn:Ca and Sr:Ca in vertebrae were determined through laser ablation inductively coupled plasma mass spectrometry. We used one-step permutational ANOVAs to evaluate multi and single-element differences in element:Ca ratios among life stages and sexes across and within sites. Element signatures differed among all sites for both single and multi-element settings. However, there were few differences among life stages within sites, except for Mn:Ca between life stages for Maranhão state, and between sexes for Sr:Ca for both Pernambuco and Rio Grande do Norte, and Ba:Ca for Rio Grande do Norte. Furthermore, all multi and single-element analyses across locations were significant and highlight the strong differences by sites. We also performed a nonmetric multidimensional scaling analysis, which demonstrated the strong differences for samples from Rio Grande do Norte and the other two sites. By analysing the lifetime transects of each sample, we observed that there was little variation in all element:Ca ratios within sites. Therefore, we argue that the longnose stingray likely does not display extensive habitat use shifts and fulfils much of its life cycle within each area. Finally, we obtained no evidence of nurseries for any site and suggest this is likely a pattern across the species distribution. Future studies investigating habitat use with samples from larger specimens (disc width > 90 cm, >15 years) are needed to better understand the species habitat use patterns across all size ranges.     

Length-weight relationship of seven bycatch fish species caught along the Chennai coast,Bay of Bengal,Eastern Indian Ocean

Length-weight relationships (LWRs) were estimated for seven fish species captured as bycatch along the Chennai coast, Bay of Bengal, Eastern Indian Ocean. Fish samples were collected fortnightly between June-2018 to February-2019 from the commercial boats operating bottom trawl nets with a cod-end mesh size of 35mm. The total length (L) and the wet weight (W) to the nearest 0.1 cm and 0.01 g, respectively which is followed by regression analysis. The values of exponent (b) for LWRs varied from 2.5803 (Parachaeturichthys polynema) to 3.4432 (Ostorhinchus oxina). Similarly, a value varied between 0.0037 (Bleekeria kallolepis) and 0.0258 (Archamia bleekeri). As per FishBase, a new TLmax has been recorded for four species such as Ostorhinchus oxina, Jaydia striata, Bleekeria kallolepis and Cocotropus roseus.     

A multi-proxy reconstruction and comparison of Holocene palaeoenvironmental changes in the Alvor and Alcantarilha estuaries (southern Portugal)

The present study investigates the history of two estuaries on the Algarve coast, southern Portugal, through a multi-proxy approach that links sedimentology, geochemistry, palynology, microfaunal analyses and radiocarbon dating. These analyses provide an overview of the development of these estuaries over the last ～7500 years. Palynological data reveal climate-driven vegetational shifts over the whole period. Microfauna, which is composed predominantly of foraminifers and ostracods, provides evidence for periods of marine and brackish water conditions, observed in both estuaries. Whereas the sediment record from the Alvor estuary shows a clear, nearly continuous silting-up sequence, the development of the Alcantarilha estuary is characterised by fluvial sedimentation, replaced by a marine environment at about 7300 yr cal BP. Marine transgression is indicated by marine-brackish foraminifera and ostracod assemblages, while upper-marsh pollen decreased and wetland communities increased at the same time. A continuous shallowing of the estuaries followed between ～6700 yr cal BP and ～5700 yr cal BP in Alvor and 4500 yr cal BP in Alcantarilha. This was interrupted by a distinct high-energy event, possibly a storm or tsunami, between 6400 and 5800 yr cal BP in Alvor; the event was not recorded in the Alcantarilha estuary. Afterwards, the silting-up restarted with clear similarities to the pre-event situation and continued until ～3500/2000 yr cal BP. This process was influenced by the build-up of sand barriers in front of the estuaries. This is also documented by a higher percentage of upper-marsh vegetation. The core from Alcantarilha estuary shows another layer of high-energy deposits, with mainly marine foraminifers and ostracods after 4500 yr cal BP. The youngest parts of the two records are characterised by decreasing tidal influence and increasing anthropogenic impact, indicated by increasing values of cultivated plants and other human-induced changes of vegetation cover.     

Walking with worms: coral‐associated epifaunal nematodes

Aims To study the community structure and habitat preferences of the Epsilonematidae and Draconematidae in coral degradation zones. To assess the contribution of different localities and microhabitats to meiobenthic diversity in such ecosystems. To discuss dispersive capacities and the occurrence of cryptic species in meiobenthic organisms. Location Porcupine Seabight (north‐east Atlantic Ocean; continental slope) and a transect along the Kenyan coast (Indian Ocean; shallow lagoon). Methods In the north‐east Atlantic, dead coral fragments, sponge skeletons and sediment were collected with a boxcorer. Along the Kenyan coast, dead coral fragments and coral gravel were collected during snorkelling and skin diving. Only nematodes belonging to the families Epsilonematidae and Draconematidae were considered. Community structure was analysed using multivariate techniques. Biodiversity was represented via rarefaction curves. Additive partitioning of species diversity was conducted. Turnover between microhabitats within locations and between locations within microhabitats were compared in a ternary plot. Results Twelve epsilonematid and five draconematid species were found in the Porcupine Seabight. In Kenya, 39 epsilonematid and 20 draconematid species were distinguished. Three species were found at both sampling locations. A table with the known distribution of all currently described species encountered in our study area is provided. At both sampling locations, the communities on coral fragments were significantly different from those in the other microhabitats, and were most diverse. In Kenya, species richness was mainly determined by local diversity and by turnover between localities. The contribution of β‐diversity decreased when abundance data were analysed. Turnover between microhabitats and between coral samples from different localities was higher than turnover between locations for gravel samples. Main conclusions Coral fragments were recognized as favourable substrata for typically epifaunal nematodes. Species‐specific habitat preferences were explained by finely tuned morphological adaptations. Our results suggest that cosmopolitan species could well be cryptic species, and this explanation for the existence of morphologically identical nematodes in geographically distant areas is weighed up against other plausible explanations. Coral degradation zones are an important source for new species of Epsilonematidae and Draconematidae. The addition of sampling locations contributed to the total number of species, although the added species were generally rare.     

Bearing Witness: Assumptions, Realities, and the Otherizing of Katrina

As post-Katrina rebuilding of Louisiana and Mississippi proceeds, we should heed the lessons from anthropologists and others studying aid and development in other parts of the world who point out that aid is often predicated on poorly examined assumptions about beneficiaries and local conditions. Hence, as the recovery after Katrina continues, assumptions about the U.S. South and about poverty, race, and class in the United States must be exposed and examined as well as assumptions about disaster victims and relief. Drawing on personal experiences, I examine here some of the assumptions with which I operated as a small group of friends and I organized an unofficial relief team to provide whatever aid we could to people on the Mississippi Gulf coast in the first few weeks after Hurricane Katrina. I recount the disconnections between my assumptions and the local conditions as relayed by Katrina survivors or that members of the team and I witnessed firsthand.     

Longer flumes increase critical swimming speeds by increasing burst–glide swimming duration in carp Cyprinus carpio, L.

Carp Cyprinus carpio altered the repertoire of swimming behaviour with increased flume length. While the transition speed from steady to burst–coast swimming was unaffected by flume length, fish reached higher critical swimming speed ( U _crit), consequently swimming for longer periods of time in burst–coast mode and hence performing more work before becoming fatigued. Analysis of swimming behaviour of burst–coast swimming revealed an increase in duration and a decrease in distance of forward burst movements with increasing water speeds. Frequency was unaffected by water speed. Overall, longer flumes increased U _crit by allowing for less restricted burst–coast swimming behaviour.