Aim We evaluated whether patterns of species diversity (α, β and γ) of rocky shore assemblages followed latitudinal gradients (i.e. LDGs) along the South American coasts, and tested hypotheses related to potential processes sustaining or disrupting the expected LDG pattern at various spatial scales. Location Coasts of South America. Taxon Macroalgae and sessile/slow‐moving macrofauna on intertidal rocky shores. Methods We evaluated changes in species composition across 143 sites. The degree of replacement and loss of species at different spatial scales (i.e. coasts, regions and sites) were estimated to help distinguish among ecological, historical and evolutionary hypotheses for explaining LDGs. Furthermore, components of diversity and taxonomic distinctness were measured, and variability in these measures was decomposed using analysis of covariance. Finally, we examined relationships between diversity and a suite of environmental and anthropogenic variables to identify potential mechanisms that may be responsible for the reported spatial relationships. Results Species composition varied with latitude, and this variability was relatively consistent on both coasts. At all spatial scales, replacement of species was the dominant phenomenon (>95%), rather than loss in the total number of species (<5%). LDGs were strongly dependent on the diversity component and the spatial scale: generally, positive for regional β‐diversity, negative for α‐diversity and site β‐diversity. Sea surface temperature (SST) was the variable that best explained patterns of diversity along both coasts (14%–22%), but other regional and local environmental variables associated with river discharges, upwelling, confluence of currents, tides and anthropogenic pressures also accounted for an important portion of variation (5%–14% each). Main conclusions Species diversity of South American rocky shores followed, with interruptions, LDGs. The trend of those LDGs, however, depended on the scale and metric used to describe diversity. It is proposed that patterns of LDGs at various scales are not the result of a single overarching process but are strongly influenced by local and regional processes. Although the most evident environmental gradient was the decrease in SST towards the south, it was demonstrated that regional and local environmental variables were also important for understanding the increase in regional β‐diversity towards the tropics.

Inbreeding, the mating between genetically related individuals, often results in reduced survival and fecundity of offspring, relative to outcrossing. Yet, high inbreeding rates are commonly observed in seaweeds, suggesting compensatory reproductive traits may affect the costs and benefits of the mating system. We experimentally manipulated inbreeding levels in controlled crossing experiments, using gametophytes from 19 populations of Macrocystis pyrifera along its Eastern Pacific coastal distribution (EPC). The objective was to investigate the effects of male–female kinship on female fecundity and fertility, to estimate inbreeding depression in the F1 progeny, and to assess the variability of these effects among different regions and habitats of the EPC. Results revealed that the presence and kinship of males had a significant effect on fecundity and fertility of female gametophytes. Females left alone or in the presence of sibling males express the highest gametophyte size, number, and size of oogonia, suggesting they were able to sense the presence and the identity of their mates before gamete contact. The opposite trend was observed for the production of embryos per female gametes, indicating higher costs of selfing and parthenogenesis than outcrossing on fertility. However, the increased fecundity compensated for the reduced fertility, leading to a stable overall reproductive output. Inbreeding also affected morphological traits of juvenile sporophytes, but not their heatwave tolerance. The male–female kinship effect was stronger in high‐latitude populations, suggesting that females from low‐latitude marginal populations might have evolved to mate with any male gamete to guarantee reproductive success.

To understand the physiological responses of the brown macroalga during the marine tidal cycle, two RNA libraries were prepared from algal frond samples collected in the intertidal zone (0 m depth) and subtidal zone (10 m depth). Samples collected from intertidal zone during low tide was considered as abiotic stressed (MI0), while samples collected from subtidal zone was considered as control (MI10). Both RNA libraries were sequenced on Illumina NextSeq 500 which generated approx. 46.9 million and 47.7 million raw paired-end reads for MI0 and MI10, respectively. Among the representative transcripts (RTs), a total of 16,398 RTs (39.20%) from MI0 and 21,646 RTs (39.24%) from MI10 were successfully annotated. A total of 535 unigenes (271 upregulated and 264 downregulated) showed significantly altered expression between MI0 and MI10. In abiotic-stressed condition (MI0), the relative expression levels of genes associated with antioxidant defenses (vanadium-dependent bromoperoxidase, glutathione S-transferase, lipoxygenase, serine/threonine-protein kinase, aspartate Aminotransferase, HSPs), water transport (aquaporin), photosynthesis (light-harvesting complex) protein were significantly upregulated, while in control condition (MI10) most of the genes predominantly involved in energy metabolism (NADH-ubiquinone oxidoreductase/NADH dehydrogenase, NAD(P)H-Nitrate reductase, long-chain acyl-CoA synthetase, udp-n-acetylglucosamine pyrophosphorylase) were overexpressed.

La estructura macrozoobentónica fue analizada durante el período de abril a setiembre de 2008. Se realizaron colectas mensuales en nueve estaciones de muestreo ubicadas en tres lagunas permanentes más características de los humedales de Ventanilla. La recolección de las muestras de sedimento se realizó con un cilindro de PVC (0,024 m 2 de área). Se determinaron las variables fisicoquímicas del agua (temperatura, oxigeno disuelto, conductividad, nitratos, coliformes totales y profundidad). La comunidad estuvo compuesta por tres filos: Annelida (Clase Oligochaeta), Artrophoda (Clase Arachnoidea y Clase Hexápoda) y Mollusca (clase Gastropoda). La abundancia promedio en las tres lagunas: Laguna Mirador (LMI), Laguna Media (LME) y Laguna Mayor (LMA) fue de 79,7, 79,9 y 605,5 individuos respectivamente. La menor abundancia se observó en el mes de abril (128 ind.) y la mayor en el mes de junio (430 ind.) decreciendo hasta setiembre (141 ind.). Los taxones más abundantes fueron Hydrobia sp y Melanoides tuberculata. Los bajos valores de diversidad (H'=1,27), riqueza (d = 0,93) y equidad (J'=0,4) es el resultado de factores que producen estrés ambiental, como la fluctuación hidrológica en los cuerpos de agua, sumado a esto las presiones antrópicas que vienen afectando al humedal. La dinámica de los macrozoobentos presentó r elación con las variables fisicoquímicas del agua.

During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays. One of the main drivers related to these mortalities was hypoxic events. This study was designed to understand the hypoxia phenomenon in these bays and to assess how the Peruvian scallop, Argopecten purpuratus, can cope with reduced oxygen levels in seawater based on individual size. First, we analyzed the relationships between dissolved oxygen saturation and other environmental parameters (the Coastal El Niño Index, temperature, salinity and pH) in bottom seawater, the frequency and intensity of hypoxic events in two main culture areas (Sechura and Paracas Bays), and their relationship with scallop mass mortalities. Then, we performed experiments with two size groups of A. purpuratus (31 and 80 mm shell height; seed and commercial size, respectively) to assess their respective survival time under severe hypoxia (1% oxygen saturation) at 16 C and a salinity of 35. Finally, the results of the field records and the experimental data are used to suggest ways to improve scallop cultivation along the Peruvian coast.