Modeling the dynamics of harmful algal bloom events in two bays from the northern Chilean upwelling system.

The bays of Tongoy and Guanaqueros are located in the Humboldt Current system, where Argopecten purpuratus has been the subject of intense aquaculture development. These bays lie in one of the most productive marine ecosystems on Earth and are dominated by permanent coastal upwelling at Lengua de Vaca Point and Choros Point, one of the three upwelling centers on the Chilean coast. Significantly, this productive system experiences a high recurrence of harmful algal bloom (HAB) events. This paper examines 9-year (2010-2018) samples of three toxic microalgal species collected in different monitoring programs and research projects. During this period, nine HAB events were detected in Guanaqueros Bay and 14 in Tongoy Bay. Among these, three HAB events were produced simultaneously in both bays by Pseudo-nitzschia australis, and two events produced simultaneously were detected in one bay by Alexandrium spp. and the other by Dinophysis acuminata. Before El Niño 2015-16, there were more HAB events of longer duration by the three species. Since El Niño, the number and duration of events were reduced and only produced by P. australis. HAB events were simulated with the FVCOM model and a virtual particle tracker model to evaluate the dynamics of bays and their relationship with HAB events. The results showed retention in bays during the relaxation conditions of upwelling and low connectivity between bays, which explains why almost no simultaneous events were recorded.

Benthic Foraminifera as Pollution Biomarkers: a Morphological Approach.

Coastal areas are often intervened by anthropic activities, which increase the contamination of toxic agents such as heavy metals. This causes adverse morphological effects on benthic microorganisms, such as foraminifera. This group is one of the most susceptible to environmental deterioration, so they can be used as pollution biomarkers by identifying shell abnormalities. Therefore, 28 sediment samples from northern Chile were analyzed, calculating the Abnormality Index-FAI and its spatio-temporal distributions in benthic foraminifera, as well as the minimum and maximum abnormality percentages and their relationship with heavy metal concentrations, using a generalized non-linear model and a principal component analysis. The results indicated a proportion of abnormal shells within the ranges described for polluted areas conditions, revealing environmental stress conditions. This reflected a change in the environmental conditions in the most recent sediments of the bay. The highest FAI values were observed to the southwest of the bay, caused by the local current system. The species Bolivina seminuda, Buliminella elegantissima, and Epistominella exigua presented a greater number of deformities, allowing them to be used as contamination biomarkers. A significant correlation was found between Ti, Mn, Ni, Va, and Ba with decreased chamber sizes, wrong coiling, scars, and number of abnormality types. This suggests the effect of the particular geochemical conditions of the area on the heavy metals that cause toxic effects on foraminifera. These analyses are an efficient tool for identifying the effects of environmental stress before they occur in higher organisms, mitigating the environmental impact on marine biodiversity.

Metal enrichment evolution in marine sediments influenced by oxygen-deficient waters in a mineral loading zone, Atacama, Chile (27° S).

This study examines metal concentrations in sediments under the influence of the oxygen minimum zone of the SE-Pacific and the anthropogenic impact following industrialization in Caldera Bay (27° S), which is one of the main ore-loading ports in operation from 1849. 210Pb and the CRS dating method were employed to estimate the age in two sediment cores sectioned at 1 cm. Metal concentrations from selected samples suggested clear impacts of industrial activities after ∼1860 on Cu, and moderate impacts on Fe, Pb, and Zn. Further, authigenic enrichment of nutrient type and redox-sensitive elements (Ni, Cd, Mo, and V) in ancient times was observed. This enrichment was related to low oxygen at the bottom and high productivity. As this condition varies over time, it could result in erroneous estimations of preindustrial values. Overall, we highlight the impact of natural processes on metal distribution in marine sediments during environmental assessments and regulations.

Stable isotopes reveal overlooked incorporation of diffuse land-based sources of nutrients and organic matter by intertidal communities at Rapa Nui (Easter Island).

Rapa Nui is an important hotspot of endemic marine biodiversity, where diffuse land-based sources (e.g., nutrients and organic matter) entering into coastal waters could develop eutrophication in coastal environments, with deleterious impacts on the marine ecosystem. Stable isotopes (δ13C and δ15N) of intertidal communities (macroalgae and invertebrates) were studied from sites with contrasting human influence (populated and unpopulated), to evaluate the incorporation and transfer of diffuse land-based sources through food webs. Macroalgae showed differences between some sites, and invertebrates showed a 15N-enrichment pattern at populated areas relative to unpopulated, being these differences significant in gastropods, barnacles and sea urchins. Moreover, trophic structure metrics suggest a higher trophic diversity in populated areas relative to unpopulated and support the isotopic partitioning between sites, associated with the incorporation of sources with 15N-enriched values. The above suggests that diffuse land-based sources could be incorporated by macroalgae, transferred into benthic consumers, and altering the trophic structure.

A new threat to local marine biodiversity: filamentous mats proliferating at mesophotic depths off Rapa Nui.

Mesophotic and deeper habitats (∼40 to 350 m in depth) around Rapa Nui (Easter Island) were investigated using a remotely operated vehicle. We observed extensive fields of filamentous cyanobacteria-like mats covering sandy substrates and mostly dead mesophotic Leptoseris spp. reefs. These mats covered up to 100% of the seafloor off Hanga Roa, the main village on the island, located on its western side. The highest mortality of corals was observed at depths between 70 and 95 m in this area. Healthy Leptoseris reefs were documented off the northern and southeastern sides of the island, which are also the least populated. A preliminary morphologic analysis of samples of the mats indicated that the assemblage is composed of at least four filamentous taxa, including two cyanobacteria (cf. Lyngbya sp. and Pseudoanabaena sp.), a brown alga (Ectocarpus sp.), and a green alga (Cladophora sp.). An ongoing eutrophication process is suggested as a potential driver of the proliferation of these filamentous mats off Hanga Roa village.

Microbial life in a fjord: metagenomic analysis of a microbial mat in Chilean patagonia.

The current study describes the taxonomic and functional composition of metagenomic sequences obtained from a filamentous microbial mat isolated from the Comau fjord, located in the northernmost part of the Chilean Patagonia. The taxonomic composition of the microbial community showed a high proportion of members of the Gammaproteobacteria, including a high number of sequences that were recruited to the genomes of Moritella marina MP-1 and Colwelliapsycherythraea 34H, suggesting the presence of populations related to these two psychrophilic bacterial species. Functional analysis of the community indicated a high proportion of genes coding for the transport and metabolism of amino acids, as well as in energy production. Among the energy production functions, we found protein-coding genes for sulfate and nitrate reduction, both processes associated with Gammaproteobacteria-related sequences. This report provides the first examination of the taxonomic composition and genetic diversity associated with these conspicuous microbial mat communities and provides a framework for future microbial studies in the Comau fjord.

Tracing the anthropogenic lead sources in coastal sediments of SE-pacific (36 degrees Lat. S) using stable lead isotopes.

This study evaluates the main sources of antropogenic Pb in one of the most industrialized centers of the southern Chilean coast (36 degrees S). Stable lead isotopes ((206)Pb/(207)Pb, (208)Pb/(207)Pb) were used to trace main Pb sources to coastal sediments, considering the suspended particulate matter (SPM) from marine (traps), continental (rivers) and industrial effluents, sediments and leaded gasoline samples. The atmospheric input was evaluated through natural collectors; i.e. Raqui-Tubul salt marsh. Results show that marine samples lie on a trend between industrial effluents ( approximately 1.16, 2.44) and natural sources (1.20, 2.50), not related to gasoline consumption. Salt marsh sediments show comparable isotopic composition to marine samples, suggesting the importance of the atmospheric input in the coastal sediments, not related to the leaded gasoline composition either. The continental input (1.18, 2.48) is highly influenced by precipitation, being difficult to separate both sources (atmosphere and continental runoff), showing also similar isotopic ratio to marine sediments. The signal of industrial emissions is masked with the introduction of Pb with higher isotopic ratios, compared to the values observed in the material collected from traps (SPM approximately 1.19, 2.48). The contribution of more radiogenic Pb by the upwelling is suggested.

Input of atmospheric lead to marine sediments in a south-east Pacific coastal area (approximately 36 degrees S).

Atmospheric input of Pb to coastal sediments in the south-east Pacific (approximately 36 degrees S) was estimated using: (1) a salt marsh (non-local emission sources) as a natural collector of atmospheric fluxes and (2) Pb concentrations in rain and air samples, both considered to be representative of the atmospheric input in the study area. A radioisotopic geochronology technique ((210)Pb) was used to estimate the total Pb atmospheric supply to the sediments. The results show that atmospheric input to Concepción Bay accounts for 13-68% of Pb in near shore sediments, evaluated through salt marsh and rain, both showing comparable results. Consequently, there are other relevant Pb sources to explain the higher concentrations in this area. Sediments in the shelf are subject to important influence of upwelling waters, estimated by Salamanca [Sources and sinks of (210)Pb in Concepción Bay, Chile (1993) PhD thesis, Marine Science Research Center, State University of New York at Stony Brook, USA] using (210)Pb. The atmospheric input, however, is mainly responsible for the total Pb input, since the salt marsh (natural atmospheric collector) shows similar Pb(xs) inventories than the shelf, corresponding to a regional-scale Pb emissions.