Migratory destinations and spatial structuring of humpback whales (Megaptera novaeangliae) wintering off Nicaragua.

Understanding the migratory patterns of large whales is of conservation importance, especially in identifying threats to specific populations. Migration ecology, including migratory destinations, movements and site fidelity for humpback whales (Megaptera novaeangliae) remain poorly studied in parts of the range of the Central America population, considered endangered under the United States Endangered Species Act. This study aimed to investigate the migratory destinations of humpback whales sighted at two study sites in Nicaragua, which are part of the Central America population. A ten-year photographic database of humpback whales observed off Nicaragua was combined with citizen science contributions and sightings from dedicated research programs. The resulting image collection was compared with available historical photo identifications and databases using an automated image recognition algorithm. This approach yielded 36 years of photographic identification totaling 431 recaptures in Nicaragua (2006-2008 and 2016-2021) and 2539 recaptures (1986-2020) in both feeding and breeding grounds of 176 unique individuals sighted in Nicaragua. Our results showed that photo-identified whales were recaptured between October and April in breeding grounds and year-round in feeding grounds between British Columbia and California, with peak recaptures between June and October. Our study provided first-time evidence on fine-scale site affinity of individual humpback whales within Nicaraguan waters and to other breeding and feeding grounds.

Assessing the ecological quality status of macrobenthic communities in a marine terminal of liquefied natural gas in Peru.

Macrobenthic organisms are useful bioindicators to assess ecological quality status. On the south-central coast of Peru (13°15.15'S, 76°18.5'W), a Liquefied Natural Gas (LNG) marine terminal has been operating since 2010. We investigated the macrobenthic communities and sediment parameters from 2011 to 2020 to evaluate the ecological quality status in the surrounding area of the marine terminal, using the AZTI Marine Biotic Index (AMBI) and its multivariate version (M-AMBI). We analyzed the diversity and community composition of macrobenthic invertebrates and the physico-chemical parameters of the sediment from 29 sampling sites, ranging from 0 to 15m depth. The sampling design considered: the direct influence zone ("DIZ", surroundings of the marine terminal), and northern (NCZ) and southern (SCZ) control zones. Our results indicated that abundance was high at SCZ and decreased with depth. Species richness and diversity were high at DIZ and NCZ, respectively, and increased up to 10m but dropped at 15m. High sand content was recorded in shallow depths, while in deeper areas and DIZ, mud and organic matter increased and redox potential was negative. AMBI indicated a "slightly disturbed" status in general, while M-AMBI indicated "good" or "moderate" status at depths ≤ 12m, and "poor" status at 15m. Overall, the season/year factor was not important, and variables were mostly significantly different across depths. Redox potential and organic matter were correlated with M-AMBI at 15m. In general, our results indicate an acceptable ecological quality surrounding the marine terminal, likely because the study area is not influenced by an important input of an anthropogenic stressor. This study highlights the importance of monitoring benthic communities in the surroundings of human-made structures and the use of ecological quality indices for understanding potential impacts.

Impacts of earthquakes and tsunamis on marine benthic communities: A review.

Marine communities are dynamic and spatially heterogeneous. Earthquakes and tsunamis modulate the structure of marine communities at short and long-term scales. The objective of this review was to evaluate how such disturbances impact the morphodynamics of coastal areas and the dynamics and structure of marine benthic communities from soft and hard bottoms from intertidal, subtidal and deep-sea habitats. The results reveal that earthquakes and tsunamis caused mortality of algae and bivalves by dissection after coastal uplift. Changes on the vertical distribution of nematodes and coral fragmentation were also recorded. Recovery of the marine communities to pre-disturbance state occurred by migration and recolonization of impacted habitats. The meiofaunal organisms recovered quickly, while some communities recovered after three years. Information pre-disturbance is often lacking or covers a short temporal extent. It is important to establish long-term monitoring programs in areas where the likelihood of impact of disturbance of such magnitude is high to understand how marine communities are shaped at geological scales.

Benthic microbial diversity trends in response to heavy metals in an oxygen-deficient eutrophic bay of the Humboldt current system offshore the Atacama Desert.

Mejillones Bay is a coastal ecosystem situated in an oxygen-deficient upwelling area impacted by mining activities in the coastal desert region of northern Chile, where conspicuous microbial life develops in the sediments. Herein, heavy metal (loid)s (HMs) such as Cu, Pb, As, Zn, Al, Fe, Cd, Mo, Ni and V as well as benthic microbial communities were studied using spectrometry and iTag-16 S rRNA sequencing. Samples were taken from two contrasting sedimentary localities in the Bay named Punta Rieles (PR) and Punta Chacaya (PC) within 10-50 m water-depth gradient. PR sediments were organic matter rich (21.1% of TOM at 50 m) and overlaid with low-oxygen waters (<0.06 ml O2/L bottom layer) compared with PC. In general, HMs like Al, Ni, Cd, As and Pb tended to increase in concentration with depth in PR, while the opposite pattern was observed in PC. In addition, PR presented a higher number of unique families (72) compared to PC (35). Among the top ten microbial families, Desulfobulbaceae (4.6% vs. 3.2%), Flavobacteriaceae (2.8% vs. 2.3%) and Anaerolineaceae (3.3% vs. 2.3%) dominated in PR, meanwhile Actinomarinales_Unclassified (8.1% vs. 4.2%) and Sandaracinaceae (4.4% vs. 2.0%) were more abundant in PC. Multivariate analyses confirmed that water depth-related variation was a good proxy for oxygen conditions and metal concentrations, explaining the structure of benthic microbial assemblages. Cd, Ni, As and Pb showed uniformly positive associations with communities that represented the keystone taxa in the co-occurrence network, including Anaerolineaceae, Thiotrichaceae, Desulfobulbaceae, Desulfarculaceae and Bacteroidales_unclassified communities. Collectively, these findings provide new insights for establishing the ecological interconnections of benthic microorganisms in response to metal contamination in a coastal upwelling environment.

Functional changes in benthic macrofaunal communities along a natural gradient of hypoxia in an upwelling system.

Increasing global concern has been raised about the expansion of hypoxia in coastal waters and its potential to impact benthic ecosystems. Upwelling areas offer opportunities to study the effects of hypoxia on benthic communities under natural conditions. We used a biological trait-based approach and estimated functional diversity indices to assess macrobenthic community functioning along a depth gradient associated with naturally increasing hypoxia and concentrations of organic matter in the upwelling zone of northern Chile (South-East Pacific) over two years. Our results highlighted the increasing dominance of opportunistic biological traits associated with hypoxia and high organic matter content. Habitat filtering was the main process affecting the studied communities. Functional diversity patterns were persistent overtime despite the occurrence of a pulse of oxygenation. This study contributes to our understanding of how natural hypoxia impacts macrobenthic communities, providing useful information in the context of increasing eutrophication due to human influence on coastal areas.

Testing for deterministic succession in metazoan parasite communities of marine fish.

Parasite communities are similar to free-living communities; decay of similarity over geographic distance, theory of island biogeography, species-area relationships and nestedness have been documented in both communities. Ecological succession has been studied in free-living communities but has rarely been examined in parasite communities. We use seriation with replication to test the hypothesis that succession of parasite community structure is deterministic, thus developing throughout consecutive changes along the fish ontogeny, via a seriated pattern. 12 306 marine fishes (95 species) were studied. In 40 species, a seriated pattern was detected; 25 had a tendency towards a seriated pattern, and for 31 species, succession was at random. Age-classes for each host species explained deterministic successional patterns for whole parasite communities and ectoparasites. Richness and number of age-classes explained this pattern for endoparasites. Seriated successional pattern was evident for parasite communities of long-lived marine fish, indicating that parasite communities follow sequential changes over time, like many free-living communities.

Biogeographical zonation of rocky intertidal communities along the coast of Peru (3.5-13.5° S Southeast Pacific).

The biogeography of the Peruvian Eastern Pacific coast has been described based on oceanographic parameters and qualitative species occurrence data. This has generated disagreement about the limits and existence of different biogeographic units. In this study, the distribution of rocky-shore macrobenthic communities were recorded over 41 sites along the Peruvian coastline (3.5°S-13.5°S) and analyzed together with historic abiotic data in order to quantitatively evaluate the biogeographic zonation of rocky intertidal communities throughout the region and its relationship with environmental variables to propose an update bioregionalization. Clusters and non-metric multidimensional scaling were performed using Bray-Curtis dissimilarity matrices from abundance data to evaluate biogeographic patterns of dissimilarities of rocky-shore communities. Significant turnover of taxa among defined biogeographical units was tested using permutational multivariate dispersion. Relationships between of the biogeographical community's structure and environmental factors were examined using Random Forest analysis on datasets available at Bio-Oracle and Jet Propulsion Laboratory-California Institute of Technology. Variation of community structure of 239 taxa depicted three biogeographical units along the region matching Panamic, transitional and Humboldt provinces. Beta diversity analysis indicated a significant turnover of taxa within the transitional unit. Random forest analysis showed a strong correlation between biogeographic units with phosphate, sea surface temperature, nitrate, dissolved oxygen, cloud fraction, and silicates. Our results set the putative limits of three biogeographic units for rocky-shore communities along the coast of Peru, providing base-line information for understanding further biogeographic changes on communities associated with the ongoing regional coastal cooling and impacts of El Niño events.

Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem.

Hypoxia is one of the most important stressors affecting the health conditions of coastal ecosystems. In highly productive ecosystems such as the Humboldt Current ecosystem, the oxygen minimum zone is an important abiotic factor modulating the structure of benthic communities over the continental shelf. Herein, we study soft-bottom macrobenthic communities along a depth gradient-at 10, 20, 30 and 50 m-for two years to understand how hypoxia affects the structure of shallow communities at two sites in Mejillones Bay (23°S) in northern Chile. We test the hypothesis that, during months with shallow hypoxic zones, community structure will be much more dissimilar, thereby depicting a clear structural gradient with depth and correlated abiotic variables (e.g. organic matter, temperature and salinity). Likewise, during conditions of deeper hypoxic zones, communities will be similar among habitats as they could develop structure via succession in conditions with less stress. Throughout the sampling period (October 2015 to October 2017), the water column was hypoxic (from 2 to 0.5ml/l O2) most of the time, reaching shallow depths of 20 to 10 m. Only one episode of oxygenation was detected in June 2016, where normoxia (>2ml/l O2) reached down to 50 m. The structure of the communities depicted a clear pattern of increasing dissimilarity from shallow normoxic and deep hypoxic habitat. This pattern was persistent throughout time despite the occurrence of an oxygenation episode. Contrasting species abundance and biomass distribution explained the gradient in structure, arguably reflecting variable levels of hypoxia adaptation, i.e. few polychaetes such as Magelona physilia and Paraprionospio pinnata were only located in low oxygen habitats. The multivariable dispersion of community composition as a proxy of beta diversity decreased significantly with depth, suggesting loss of community structure and variability when transitioning from normoxic to hypoxic conditions. Our results show the presence of semi-permanent shallow hypoxia at Mejillones Bay, constraining diverse and more variable communities at a very shallow depth (10-20 m). These results must be considered in the context of the current decline of dissolved oxygen in most oceans and coastal regions and their impact on seabed biota.

Breaking out of the comfort zone: El Niño-Southern Oscillation as a driver of trophic flows in a benthic consumer of the Humboldt Current ecosystem.

The trophic flow of a species is considered a characteristic trait reflecting its trophic position and function in the ecosystem and its interaction with the environment. However, climate patterns are changing and we ignore how patterns of trophic flow are being affected. In the Humboldt Current ecosystem, arguably one of the most productive marine systems, El Niño-Southern Oscillation is the main source of interannual and longer-term variability. To assess the effect of this variability on trophic flow we built a 16-year series of mass-specific somatic production rate (P/B) of the Peruvian scallop (Argopecten purpuratus), a species belonging to a former tropical fauna that thrived in this cold ecosystem. A strong increase of the P/B ratio of this species was observed during nutrient-poor, warmer water conditions typical of El Niño, owing to the massive recruitment of fast-growing juvenile scallops. Trophic ecology theory predicts that when primary production is nutrient limited, the trophic flow of organisms occupying low trophic levels should be constrained (bottom-up control). For former tropical fauna thriving in cold, productive upwelling coastal zones, a short time of low food conditions but warm waters during El Niño could be sufficient to waken their ancestral biological features and display massive proliferations.

First record of hybridization between green Chelonia mydas and hawksbill Eretmochelys imbricata sea turtles in the Southeast Pacific.

Hybridization among sea turtle species has been widely reported in the Atlantic Ocean, but their detection in the Pacific Ocean is limited to just two individual hybrid turtles, in the northern hemisphere. Herein, we report, for the first time in the southeast Pacific, the presence of a sea turtle hybrid between the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata. This juvenile sea turtle was captured in northern Peru (4°13'S; 81°10'W) on the 5(th) of January, 2014. The individual exhibited morphological characteristics of C. mydas such as dark green coloration, single pair of pre-frontal scales, four post-orbital scales, and mandibular median ridge, while the presence of two claws in each frontal flipper, and elongated snout resembled the features of E. imbricata. In addition to morphological evidence, we confirmed the hybrid status of this animal using genetic analysis of the mitochondrial gene cytochrome oxidase I, which revealed that the hybrid individual resulted from the cross between a female E. imbricata and a male C. mydas. Our report extends the geographical range of occurrence of hybrid sea turtles in the Pacific Ocean, and is a significant observation of interspecific breeding between one of the world's most critically endangered populations of sea turtles, the east Pacific E. imbricata, and a relatively healthy population, the east Pacific C. mydas.

The elusive life cycle of scyphozoan jellyfish--metagenesis revisited.

Massive proliferations of scyphozoan jellyfish considerably affect human industries and irreversibly change food webs. Efforts to understand the role of jellyfish in marine ecosystems are based on a life cycle model described 200 years ago. According to this paradigm the pelagic medusae is considered seasonal and alternates with the benthic polyp stage from which it derives. However, we provide evidence that a) the occurrence of several species of medusae is not restricted to a season in the year, they overwinter, b) polyp- and medusa generations are neither temporally nor spatially separated, and c) "metagenesis" which is defined as the alternation between sexual and asexual generations does not always occur. Hence we recommend additions to the current model and argue that the scyphozoan life cycle should be considered multi-modal, rather than metagenetic. The implications of these findings for jellyfish proliferations, including possible consequences and associated environmental drivers, are discussed.

Fast growing, healthy and resident green turtles (Chelonia mydas) at two neritic sites in the central and northern coast of Peru: implications for conservation.

In order to enhance protection and conservation strategies for endangered green turtles (Chelonia mydas), the identification of neritic habitats where this species aggregates is mandatory. Herein, we present new information about the population parameters and residence time of two neritic aggregations from 2010 to 2013; one in an upwelling dominated site (Paracas ∼14°S) and the other in an ecotone zone from upwelling to warm equatorial conditions (El Ñuro ∼4°S) in the Southeast Pacific. We predicted proportionally more adult individuals would occur in the ecotone site; whereas in the site dominated by an upwelling juvenile individuals would predominate. At El Ñuro, the population was composed by (15.3%) of juveniles, (74.9%) sub-adults, and (9.8%) adults, with an adult sex ratio of 1.16 males per female. Times of residence in the area ranged between a minimum of 121 and a maximum of 1015 days (mean 331.1 days). At Paracas the population was composed by (72%) of juveniles and (28%) sub-adults, no adults were recorded, thus supporting the development habitat hypothesis stating that throughout the neritic distribution there are sites exclusively occupied by juveniles. Residence time ranged between a minimum of 65 days and a maximum of 680 days (mean 236.1). High growth rates and body condition index values were estimated suggesting healthy individuals at both study sites. The population traits recorded at both sites suggested that conditions found in Peruvian neritic waters may contribute to the recovery of South Pacific green turtles. However, both aggregations are still at jeopardy due to pollution, bycatch and illegal catch and thus require immediate enforcing of conservation measurements.

Patterns of spatial and temporal distribution of humpback whales at the southern limit of the Southeast Pacific breeding area.

Understanding the patterns of spatial and temporal distribution in threshold habitats of highly migratory and endangered species is important for understanding their habitat requirements and recovery trends. Herein, we present new data about the distribution of humpback whales (Megaptera novaeangliae) in neritic waters off the northern coast of Peru: an area that constitutes a transitional path from cold, upwelling waters to warm equatorial waters where the breeding habitat is located. Data was collected during four consecutive austral winter/spring seasons from 2010 to 2013, using whale-watching boats as platforms for research. A total of 1048 whales distributed between 487 groups were sighted. The spatial distribution of humpbacks resembled the characteristic segregation of whale groups according to their size/age class and social context in breeding habitats; mother and calf pairs were present in very shallow waters close to the coast, while dyads, trios or more whales were widely distributed from shallow to moderate depths over the continental shelf break. Sea surface temperatures (range: 18.2-25.9°C) in coastal waters were slightly colder than those closer to the oceanic realm, likely due to the influence of cold upwelled waters from the Humboldt Current system. Our results provide new evidence of the southward extension of the breeding region of humpback whales in the Southeast Pacific. Integrating this information with the knowledge from the rest of the breeding region and foraging grounds would enhance our current understanding of population dynamics and recovery trends of this species.

Regulatory factors and structure of a component population of the spionid Polydora bioccipitalis infesting the surf clam Mesodesma donacium.

Spionidae, particularly polydorids, are common polychaete parasites of edible mollusks around the world. However, our understanding of the regulatory factors and population structure of these parasites is scant. In this study involving Polydora bioccipitalis and the surf clam Mesodesma donacium we evaluated (1) the environmental correlates of the prevalence and mean intensity of the infestation, (2) the relationship between the number of egg capsules and juvenile and adult parasites and the time elapsed since infestation, and (3) the spatial patterns of juveniles and adults within the host. Environmental factors showed no significant correlations with prevalence and mean intensity, suggesting that these factors do not act directly as regulators. Rather, storm surges seemingly induced clam stranding, which in turn affected both the prevalence and intensity of the infestation. The numbers of juveniles and egg capsules in blisters were significantly related to the time since infestation, suggesting mechanisms of use and expansion of the space within the host. Juvenile worms showed an aggregated distribution that was probably related to the episodic nature of infestation events, whereas adults exhibited uniform distributions that probably reflect territorial behavior and reproductive strategies.