Since November of 2015, when ore tailings from a dam rupture reached the Atlantic Ocean, researchers are trying to assess the degree of impact across the Doce River and adjacent coastal area. This study aims to use the zooplankton dynamics as a tool to evaluate the environmental impact in the coastal region, five years after the rupture, during periods of low and high river flow. Doce River flow varied from 49 to 5179 m ³/s and structured the zooplankton community between periods of low and high river flow, but salinity and chlorophyll-a had stronger correlation with depth (r = 0.40 and − 0.40 respectively) than with the Doce River discharge variation along the sampling period (r < 0.2). On the other hand, inorganic particles in the water and total metal concentration (dissolved + particulate), used as tracers of the iron enriched tailing (Al, Cd, Cr, Cu, Fe, V), were correlated with fluvial discharge and showed to be the main factor driving the zooplankton community dynamics. For assessing the degree of environmental impact, we tested the ecological indexes for the zooplankton community. Margalef Richness, Pielou Evenness and Shannon-Wiener Diversity varied from 2.52, 0.40 and 1.39 (all registered during high river flow period) to 9.02, 0.85 and 3.44 (all registered during low river flow period), respectively. Along with those community indicators, we evaluated the response of representative taxonomical genera such as Paracalanus, Oikopleura and Temora, regarding the Doce River flow, and found population patterns that established a baseline for future monitoring in the region. Our results showed that the zooplankton community is more fragile when the river discharge is stronger, and this pattern is confirmed by all indicators tested.

Paq proxy was applied on mid and long-chain n-alkanes in order to develop an index to assist in the long-term assessment of changes and exchanges between aquatic communities in estuarine environments as a result of increased saline incursion. New boundaries are proposed according to n-alkanes abundance in the leaves of local mangrove tree species for better definition of emergent aquatic plant end-member. Molecular distribution and δ13C isotopic signatures of n-alkanes were also used to support the parameter. A predominance of odd carbon-numbered long chain (> C27 n-alkanes) indicated a main terrestrial input, although mid-chain n-alkanes (23 and 25 carbons) were also identified. Short-chain n-alkanes (< 19) were absent or found in a very small concentration. Carbon Preference Index and C/N ratio reinforced a terrestrial origin for the sedimentary organic matter. δ13C signatures of n-alkanes for C23, C25, C29 and C31 were characteristic of mangrove input, ranging from -27.57 ‰ (C23) to -34.40 ‰ (C29) for Piraquê-Mirim River (PM) and from -27.36 ‰ (C23) to -32.84 ‰ (C31) for Piraquê-Açu River (PA) without any particular trend. Paq proxy was successfully used to identify rises in marine macrophytes (mid-chain n-alkanes) input mainly in the confluence and PM probably as consequence of drought periods. The confluence presented a mixing sources of OM. PA was identified as a stable mangrove environment while PM was characterized by pulses of marine macrophytes input and should be managed with care in respect to its catchment for water use and dam constructions as a shortage of fresh water can alter the estuarine ecology.

The present work evaluate the molecular and isotopic composition of n-alkanes from mangrove species Rizophora mangle (RZ), Laguncularia racemosa (LA) and Avicennia schaueriana (AV) at Mangrove Biological Reserve of Piraquê-Açu and Piraquê-Mirim rivers (Aracruz-ES/Brazil). The n-alkanes total concentrations ranged from 0.89 (R. mangle green leaf) to 398.67 ug.g-1 dry weight (A. schaueriana, senescent leaf), been the senescent leaves having the most abundance independent from specie. The CPI (Carbon Preference Index) values were in the proposed limit for terrestrial plants waxes, where the average between senescent and green leaves from each species were RZ = 6,70; LA = 20,73; and AV = 8,30. The δ13C from C25 to C31 n-alkanes average values indicated a pattern distribution based on saline and hydric stress (L. racemosa = -36.94; R. mangle = -35.98; A. schaueriana = -35.03‰).

Estuaries are coastal environments that normally accumulate many contaminants in their sediments, where the estuary of the Canal da Passagem (Vitória-ES) falls in this type of coastal environment, because it is a region that has been suffering with urbanization and industrialization around. In order to evaluate the quality of the sediment of the estuary, were analyzed trace metals cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), Scandium (Sc) and Zinc (Zn), hydrocarbons (n-alkanes and hopanes), organic carbon and total nitrogen ratio (Corg/Ntotal) and stable isotopes (δ13C) in 3 sediment cores (P1, P2 and P3). The metal concentrations ranged from 0.06 to 0.93 μg/g (Cd) 4.03 to 63.45 μg/g (Cr) 1.27 to 32.72 μg/g (Cu), 1.12 - 10, 05 μg / g (Ni), 1.69 to 22.85 μg/g (Pb), 0.62 to 4.29 μg/g (Sc) and 19.62 to 166.17 μg/g (Zn).The concentrations hydrocarbon were 0.29 to 32.50 μg/g for the n-alkanes and from 0.06 to 14.44 μg/g for the hopanes. While the values of Corg/Ntotal and δ13C varied from 12.96 to 60.96, -36.20 to -25.01‰, respectively. The results show that the estuary of the Canal da Passagem has suffered an accumulation of pollutants over time, especially in the region of core P1, which showed characteristics of anthropogenic contribution to the contamination with oil and derivatives being the main source of metals and hopanes.