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An updated molecular phylogeny of the blenny genus Ophioblennius, with a focus on two geographically disjunct morphotypes observed in Brazil, is presented. The analyses showed that specimens from the north-eastern Brazilian coast are the endemic redlip blenny Ophioblennius trinitatis, but specimens from the southern Brazilian coast are conspecific to an undescribed east Atlantic Ocean (Gulf of Guinea) species, previously unknown in Brazil. Possible explanations for this geographical pattern include: natural larval dispersal and rafting across the Atlantic; an unknown ecological attribute that enabled this species to colonize southern Brazil; oil platforms as introduction vectors.

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Dispersal on floating seaweeds depends on availability, viability, and trajectories of the rafts. In the southern hemisphere, the bull kelp Durvillaea antarctica is one of the most common floating seaweeds, but phylogeographic studies had shown low connectivity between populations from continental Chile, which could be due to limitations in local supply and dispersal of floating kelps. To test this hypothesis, the spatiotemporal dynamics of kelp strandings were examined in four biogeographic districts along the Chilean coast (28°-42°S). We determined the biomass and demography of stranded individuals on 33 beaches for three subsequent years (2013, 2014, 2015) to examine whether rafting is restricted to certain districts and seasons (winter or summer). Stranded kelps were found on all beaches. Most kelps had only one stipe (one individual), although we also frequently found coalesced holdfasts with mature males and females, which would facilitate successful rafting dispersal, gamete release, and reproduction upon arrival. High biomasses of stranded kelps occurred in the northern-central (30°S-33°S) and southernmost districts (37°S-42°S), and lower biomasses in the northernmost (28°S-30°S) and southern-central districts (33°S-37°S). The highest percentages and sizes of epibionts (Lepas spp.), indicative of prolonged floating periods, were found on stranded kelps in the northernmost and southernmost districts. Based on these results, we conclude that rafting dispersal can vary regionally, being more common in the northernmost and southernmost districts, depending on intrinsic (seaweed biology) and extrinsic factors (shore morphology and oceanography) that affect local supply of kelps and regional hydrodynamics.

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Large rivers create major gaps in reef distribution along tropical shelves. The Amazon River represents 20% of the global riverine discharge to the ocean, generating up to a 1.3 × 10(6)-km(2) plume, and extensive muddy bottoms in the equatorial margin of South America. As a result, a wide area of the tropical North Atlantic is heavily affected in terms of salinity, pH, light penetration, and sedimentation. Such unfavorable conditions were thought to imprint a major gap in Western Atlantic reefs. We present an extensive carbonate system off the Amazon mouth, underneath the river plume. Significant carbonate sedimentation occurred during lowstand sea level, and still occurs in the outer shelf, resulting in complex hard-bottom topography. A permanent near-bottom wedge of ocean water, together with the seasonal nature of the plume's eastward retroflection, conditions the existence of this extensive (~9500 km(2)) hard-bottom mosaic. The Amazon reefs transition from accretive to erosional structures and encompass extensive rhodolith beds. Carbonate structures function as a connectivity corridor for wide depth-ranging reef-associated species, being heavily colonized by large sponges and other structure-forming filter feeders that dwell under low light and high levels of particulates. The oxycline between the plume and subplume is associated with chemoautotrophic and anaerobic microbial metabolisms. The system described here provides several insights about the responses of tropical reefs to suboptimal and marginal reef-building conditions, which are accelerating worldwide due to global changes.

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Distribution of the mangrove gastropods Neritina virginea (Neritidae) and Littoraria angulifera (Littorinidae) within the Colombian Caribbean Darién Ecoregion. Gastropods are one of the most abundant groups within the Caribbean mangroves, however, little is known about the distribution of particular species at a regional scale. With this aim, we studied the geographic distribution of Littoraria (Littorinopsis) angulifera and Neritina (Vitta) virginea within the Darién Ecoregion in the Caribbean coast of Colombia, from 77 sampling stations along 609km between the Colombian-Panamá border and Córdoba State, Colombia. The fieldwork was conducted in June-August 2009, and a total of 3 963 individuals of both species were hand-picked from the ground, prop-roots and trunks along 50m transects, and shell sizes were measured. The description of geographic patterns considered surface water salinity, mangrove cover and gastropod distribution within the Gulf of Urabá. In the outer-most part of the Gulf, L. angulifera was present in 84.8% of the stations, while N. virginea was only present in 15.2% of the stations. In this part, mangroves areas were patchily distributed, and the gastropods (mainly L. angulifera) were found on woody debris along the supralittoral zone in sandy shores. In the inner-most part, in contrast, N. virginea occurred in 84.6% of the stations, mostly in estuaries, deltas and river margins, while L. angulifera only appeared in Turbo Bay (15.4%). Mean shell size also exhibited a clear geographic pattern: size range was 6-22mm in L. angulifera, and 6-12mm in N. virginea. L. angulifera was found in open-water stations with water salinities >10PSU, but it was absent in sites with lower salinities like the Atrato River Delta and other small rivers. Its presence on coastal woody debris suggests that despite of the recruitment of small individuals from the nearshore stock of larvae, populations are unable to establish due to the absence of mangroves protection. Oppositely, N. virginea was found under estuarine conditions on mangrove roots and ground. Our results confirm that L. angulifera is an esteno-tolerant marine species, and N. virginea is an eury-tolerant estuarine species, thus their geographic distribution is strongly shaped by the large freshwater discharge of the Atrato River. We hypothesize that absence or limited distribution of gastropods in various areas of the Darién Ecoregion may be further explained by the poor conservation state of mangroves.

Aunque los gasterópodos son uno de los grupos más abundantes en los manglares del Caribe, poco se sabe del ámbito de especies particulares debido al enfoque comunitario de la mayoría de los estudios. El ámbito de las poblaciones de L. angulifera y N. virginea fue estudiado en la Ecorregión Darién, Caribe colombiano. El muestreo se realizó entre junio y agosto 2009, se recolectaron 3 963 individuos de ambas especies, a los cuales se les midió la talla de la concha. La Ecorregión presentó diferencias espaciales en el ámbito de la salinidad del agua a nivel superficial, la cobertura de manglar y el ámbito de las poblaciones. En la parte externa de la Ecorregión, L. angulifera presentó el mayor porcentaje de aparición (84.8%) en comparación a N. virginea (15.2%). En el interior N. virginea presentó el mayor porcentaje (84.6%), mientras L. angulifera apareció solo en bahía Turbo (15.4%). Se encontraron diferencias en el ámbito de tallas promedio de las conchas, donde L. angulifera varió entre 6 y 22mm y N. virginea entre 6 y 12mm dentro del Golfo. Se confirma que L. angulifera es una especie de carácter estenohalina y marina, mientras que N. virginea es eurihalina y estuarina.

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