Finding the needle in a haystack: Evaluation of ecotoxicological effects along the continental shelf break during the Brazilian mysterious oil spill.

Oceanic oil spills present significant ecological risks that have the potential to contaminate extensive areas, including coastal regions. The occurrence of the 2019 oil spill event in Brazil resulted in over 3000 km of contaminated beaches and shorelines. While assessing the impact on benthic and beach ecosystems is relatively straightforward due to direct accessibility, evaluating the ecotoxicological effects of open ocean oil spills on the pelagic community is a complex task. Difficulties are associated with the logistical challenges of responding promptly and, in case of the Brazilian mysterious oil spill, to the subsurface propagation of the oil that impeded remote visual detection. An oceanographic expedition was conducted in order to detect and evaluate the impact of this oil spill event along the north-eastern Brazilian continental shelf. The pursuit of dissolved and dispersed oil compounds was accomplished by standard oceanographic methods including seawater polycyclic aromatic hydrocarbons (PAHs) analysis, biomass stable carbon isotope (δ13C), particulate organic carbon to particulate organic nitrogen (POC:PON) ratios, nutrient analysis and ecotoxicological bioassays using the naupliar phase of the copepod Tisbe biminiensis. Significant ecotoxicological effects, reducing naupliar development by 20-40 %, were indicated to be caused by the presence of dispersed oil in the open ocean. The heterogeneous distribution of oil droplets aggravated the direct detection and biochemical indicators for oil are presented and discussed. Our findings serve as a case study for identifying and tracing subsurface propagation of oil, demonstrating the feasibility of utilizing standard oceanographic and ecotoxicological methods to assess the impacts of oil spill events in the open ocean. Ultimately, it encourages the establishment of appropriate measures and responses regarding the liability and regulation of entities to be held accountable for oil spills in the marine environment.

Daily variability of pH and temperature in seawater from a near-pristine oceanic atoll, Southwest Atlantic.

The study of pH and temperature variability in reef environments, and the underlying processes that control this variability, is of great importance for ocean acidification research. Therefore, in the reef environment of Rocas Atoll, we conducted continuous monitoring of pH and temperature and periodic sampling of carbonate chemistry, and we hypothesize that seawater temperature is not the determining factor in the daily variability of pH at this atoll. Our results showed that the seawater of the atoll presented a high daily variability in pH, [H+], and temperature. The cycles of variations occurred primarily with a periodicity of ∼24 h, related to the daily light cycle, and secondarily with a periodicity of ∼12 h, associated with the semi-diurnal tidal cycles of the atoll. The results indicate that the relative balance of net organic carbon metabolism is the main process modulating carbonate chemistry on the atoll throughout the day.

Secondary production of Acartia tonsa Dana, 1849 and A. lilljeborgii Giesbrecht, 1889 in an Amazonian estuary (Brazil).

The dynamics of the copepods A. tonsa and A. lilljeborgii were described for the first time in the Taperaçu Estuary. The acartiids were collected using plankton nets (200 µm) in June 2012, March 2013 (rainy season) and September 2012 and 2013 (dry season). The oscillations in rainfall and the fluctuations in hydrological variables influenced the abundance, biomass, and production of both A. tonsa (17 ± 23 to 8501 ± 13,248 ind.m-3; 16,385.29 mg.C.m-3; 0.09 ± 0.21 to 355.17 ± 590.84 mg.C.m-3.d-1) and A. lilljeborgii (14 ± 11 to 1470 ± 1591 ind.m-3; 22,398.40 mg.C.m-3; 177.99 ± 263.13 mg.C.m-3.d-1) with clear monthly, seasonal, and spatial patterns. The high levels of production observed may be related to the presence of waters rich in particulate organic material derived from the adjacent mangrove forests. This material is consumed by a number of copepod species, in particular A. tonsa and A. lilljeborgii, favoring the development and reproduction of both species which are characterized by high rates of productivity in the study estuary. The present results indicate that the biomass and productivity in equatorial mangrove estuaries may be relatively high in comparison with the levels observed in other coastal systems around the world and that earlier stages of both species have a great relevance for biomass and production in Amazonian estuaries.

Evidence for enhanced primary production driving significant CO2 drawdown associated with the Atlantic ITCZ.

The intense rainfall associated with the Intertropical Convergence Zone (ITCZ), a narrow zone of confluence of the northeast and southeast trades, can significantly alter sea surface salinity, the chemistry of inorganic C and the resulting sea-air CO2 exchange in the tropics. We have analyzed extensive underway data collected from 2008 until 2014 and recorded by an autonomous CO2 system installed on a commercial ship that crosses the central tropical Atlantic (5°S to 15°N, 18°W to 36°W) to disentangle the effects of the ITCZ over the carbonate system there. Based on statistically significant linear co-variance of sea surface fugacity of CO2 (fCO2sw) and sea surface salinity in the areas affected by the ITCZ, we calculated CO2 drawdown rates associated with the impact of the ITCZ in the central tropical Atlantic ranging from 0.11 ± 0.02 to 2.35 ± 0.08 mmol m-2 d-1. These were calculated by comparing the observed fCO2sw with that expected without surface seawater carbonate system dilution and increase in gas transfer caused by the ITCZ. The observed decrease in fCO2sw associated with the freshening caused by the ITCZ is much larger than expected from thermodynamics alone. 59.1 ± 4.1 % of the total observed CO2 drawdown associated with the ITCZ cannot be explained by abiotic processes. Instead, we found significant negative correlations between underway sea surface salinity and remote-sensed chlorophyll a in the areas affected by the ITCZ. Different to other tropical oceanic basins, the tropical Atlantic receives large amounts of continental dust originated from Africa. Wet dust deposition driven by the ITCZ appears associated with the interannual variability of the CO2 drawdown associated with the ITCZ. Fertilization driven by the ITCZ seems to enhance primary production in the otherwise oligotrophic tropical Atlantic, thus significantly lowering CO2 emissions to the atmosphere.

Cellular accumulation of crude oil compounds reduces the competitive fitness of the coral symbiont Symbiodinium glynnii.

Oil spill events in the marine environment can have a deleterious impact on the affected ecosystems, such as coral reefs, with direct consequences for their socioeconomic value. The mutualistic relationship between tropical corals and their dinoflagellate symbionts (Symbiodiniaceae) provide structural and nutritional basis for a high local biodiversity in oligotrophic waters. Here, we investigated effects of crude oil water-accommodated fraction on the competitive fitness of the model zooxanthellae species Symbiodinium glynnii. Results of laboratory essays demonstrate that crude oil carbon is incorporated into the cellular biomass with a concomitant change of δ13C isotopic value. Carcinogenic/mutagenic polycyclic aromatic hydrocarbons were identified in the culture media and were responsible for a linear reduction in population growth of S. glynnii, presumably related to energy relocation for DNA repair. Additionally, the experiments revealed that physiological effects induced by crude oil compounds are genetically inherited by the following generations under non-contaminated growth conditions, and induce a reduction in the competitive fitness to cope with other environmental parameters, such as low salinity. We suggest that the effects of crude oil contamination represent an imparing factor for S. glynnii coping with anthropogenic drivers (e.g. warming and acidification) and interfere with the delicate symbiont-host relationship of tropical corals. This is especially relevant in the coastal areas of northeastern Brazil where an oil spill event deposited crude oil on shallow water sediments with the potential to be resuspended to the water column by physical and/or biological activity, enhancing the risk of future coral bleaching events.

Morphological abnormalities in Acartia lilljeborgii Giesbrecht (1889) (Copepoda, Calanoida) in a tropical estuary under industrial development.

Morphological abnormalities in crustaceans have been registered and several are attributed to pollution and others anthropogenic activities. This study reports for the first time a temporal record of the amount and variety of morphological abnormalities in Acartia lilljeborgii, in an impacted neotropical estuary. The specimens were obtained from Suape port area, Northeast Brazil, between May 2009 and September 2010 using a 300 µm plankton net. Seven types of abnormalities were observed in one of the terminal spines of the prosome, but no temporal variation of abnormalities was found in our study. The deformities were registered in 85.7% of samples and they were found in up to 10% of the individuals (3.2 ± 2.9%). The proportion of females with abnormalities was greater than for males, in opposite to most previous reports. Due to its high distribution and abundance in part of the neotropical Atlantic coastal area, A. lilljeborgii has the potential to be used as a bioindicator of environmental conditions, although the reasons of the abnormality occurrences should be accurately investigated.

Trophic dynamics (Dissolved Inorganic Nitrogen-DIN and Dissolved Inorganic Phosphorus-DIP) in tropical urban estuarine systems during periods of high and low river discharge rates.

This paper focused on the use of the biogeochemical LOICZ (Land Ocean Interactions in the Coastal Zone) to investigate the dynamics of DIN and DIP nutrients among three highly urbanized tropical estuaries (Barra das Jangadas (BJ), Recife (RE) and Timbó (TB)), located in the northeastern region of Brazil. The input data were obtained through in situ measurements (2007) and governmental agency databases (2001-2007). The balances of the non-conservative elements showed that the RE and TB systems alternated between sources and sinks during the observation periods (0.2-0.8 mmoles DIP m-2 d-1 and 0.1-10 mmoles DIN m-2 d-1). The metabolism rates in the systems indicated that the BJ system was autotrophic during the two observation periods (10-26 mmoles C m-2 d-1), while the RE system was heterotrophic (9-12 mmoles C m-2 d-1). The river discharge rates observed during the period 2001-2007 showed averages ranging from 9.4±3.8 to 18.4±7.7 m3s-1. Measurements of the trophic status in the RE system during 2007 characterized the system as eutrophic, thereby demonstrating high levels of chlorophyll-a and inorganic nutrients. The applications of balance sheets modeling proved to be very useful toward understanding the dynamics of estuarine systems dominated by large urban centers.

A Synoptic Assessment of the Amazon River-Ocean Continuum during Boreal Autumn: From Physics to Plankton Communities and Carbon Flux.

The Amazon generates the world's largest offshore river plume, which covers extensive areas of the tropical Atlantic. The data and samples in this study were obtained during the oceanographic cruise Camadas Finas III in October 2012 along the Amazon River-Ocean Continuum (AROC). The cruise occurred during boreal autumn, when the river plume reaches its maximum eastward extent. In this study, we examine the links between physics, biogeochemistry and plankton community structure along the AROC. Hydrographic results showed very different conditions, ranging from shallow well-mixed coastal waters to offshore areas, where low salinity Amazonian waters mix with open ocean waters. Nutrients, mainly [Formula: see text] and [Formula: see text], were highly depleted in coastal regions, and the magnitude of primary production was greater than that of respiration (negative apparent oxygen utilization). In terms of phytoplankton groups, diatoms dominated the region from the river mouth to the edge of the area affected by the North Brazil Current (NBC) retroflection (with chlorophyll a concentrations ranging from 0.02 to 0.94 mg m-3). The North Equatorial Counter Current (NECC) region, east of retroflection, is fully oligotrophic and the most representative groups are Cyanobacteria and dinoflagellates. Additionally, in this region, blooms of cyanophyte species were associated with diatoms and Mesozooplankton (copepods). A total of 178 zooplankton taxa were observed in this area, with Copepoda being the most diverse and abundant group. Two different zooplankton communities were identified: a low-diversity, high-abundance coastal community and a high-diversity, low-abundance oceanic community offshore. The CO2 fugacity (fCO2sw), calculated from total alkalinity (1,450 < TA < 2,394 µmol kg-1) and dissolved inorganic carbon (1,303 < DIC < 2,062 µmol kg-1) measurements, confirms that the Amazon River plume is a sink of atmospheric CO2 in areas with salinities <35 psu, whereas, in regions with salinities >35 and higher-intensity winds, the CO2 flux is reversed. Lower fCO2sw values were observed in the NECC area. The ΔfCO2 in this region was less than 5 µatm (-0.3 mmol m-2 d-1), while the ΔfCO2 in the coastal region was approximately 50 µatm (+3.7 mmol m-2 d-1). During the cruise, heterotrophic and autotrophic processes were observed and are indicative of the influences of terrestrial material and biological activity, respectively.

Eutrophication effects on phytoplankton size-fractioned biomass and production at a tropical estuary.

Size-fractioned phytoplankton (pico, nano and microplankton) biomass and production were estimated throughout a year at Recife harbor (NE Brazil), a shallow well mixed tropical hypereutrophic estuary with short residence times but restricted water renewal. Intense loads of P-PO4 (maximum 14 µM) resulted in low N:P ratios (around 2:1), high phytoplankton biomass (B=7.1-72 µg chl-a L(-1)), production (PP=10-2657 µg C L(-1) h(-1)) and photosynthetic efficiency (P(B)=0.5-45 µg C µg chl-a(-1)), but no oxygen depletion (average O2 saturation: 109.6%). Nanoplankton dominated phytoplankton biomass (66%) but micro- and nanoplankton performed equivalent primary production rates (47% each). Production-biomass models indicate an export of the exceeding microplankton biomass during most of the year, possibly through grazing. The intense and constant nutrient and organic matter loading at Recife harbor is thus supporting the high microplankton productivity that is not accumulating on the system nor contributing to oxygen depletion, but supporting the whole system's trophic web.