Benthic foraminifera as bioindicators of potentially toxic element (PTE) pollution: Torrecillas lago

Ecological Indicators 89 (2018) 516–527

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Original Articles

Benthic foraminifera as bioindicators of potentially toxic element (PTE) pollution: Torrecillas lagoon (San Juan Bay Estuary), Puerto Rico

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Michael Martínez-Colóna,⁎, Pamela Hallockb, Carlos R. Green-Ruízc, Joseph M. Smoakd a

School of the Environment, Florida A&M University, FSH Science Research Center (RM306B), 1515 South MLK Blvd., Tallahassee, FL, 32307, United States College of Marine Science, University of South Florida, 830 1st Street South, St. Petersburg, FL, 33701, United States c Instituto de Ciencias del Mar Limnología, Universidad Autónoma de México, Ave. Joel Montes Camarena s/n, 82000, Mazatlán, Sinaloa, Mexico d Environmental Science, University of South Florida, 140 7th Ave South,St. Petersburg, FL, 33701, United States b

A R T I C L E I N F O

A B S T R A C T

Keywords: Heavy metals Ecology Caribbean Bioavailability Hypoxia

Torrecillas Lagoon, on the north coast of Puerto Rico, has experienced extensive anthropogenic influence over the past 200 years. Elevated concentrations of Potentially Toxic Elements (PTEs) in bulk sediment (Cu, Zn, Pb, Ni, Cr, Li, V, Fe, As, Se, and Mn) have been reported in surficial sediments and have relatively uniform spatial distributions. Areas with higher concentrations are associated with a higher percentage of total organic carbon (TOC) and percent mud (mud), as well as anoxic conditions. Ammonia beccarii, Quinqueloculina rhodiensis, and Triloculina oblonga are the dominant foraminifers in the lagoon and are characteristic of stressed coastal environments. Bulk concentrations of Cu-Zn-Fe are negatively correlated with numerous foraminiferal taxa, absolute abundances, and diversity indices, though very few correlations with the bioavailable counterparts (F2Tess-bioavailable) are observed. Similarly, relative abundances of Quinqueloculina and Triloculina positively correlate with bulk Cu-Zn-Fe but not with F2Tess-bioavailable. The waters in Torrecillas lagoon show strong stratification, with hypoxic/anoxic (dissolved oxygen <3 mg/L) and corrosive (pH < 7.4) conditions below 4 m depth. The presence of such strong gradients in very shallow water represents a dynamic chemical environment, with changes occurring on day-night cycles, tidal cycles, and especially with storm activity that induces mixing of otherwise highly stratified, very localized waters. Recognizing the potential for sequestered PTEs to be remobilized is an essential insight for coastal management agencies that must assess the risks of existing PTEs during coastal engineering activities (e.g., dredge and fill activities) and major storm events. Exchangeable and oxidizable fractions are likely more bioavailable than acid-soluble fractions in influencing the ecology of foraminifers under most circumstances.

1. Introduction Estuaries are experiencing adverse changes that are influencing the natural variability of these unique ecosystems. Coastal lagoons commonly serve as sinks for a wide range of pollutants (Zaaboub et al., 2015). Rapid industrialization, overpopulation, surface-water alteration, and other factors are changing estuarine environments and biotic communities (e.g., Green-Ruíz et al., 2005; Hunter and Arbona, 1995). Estuaries receive approximately 80–90% of all waste released to marine environments (Gross, 1978) and therefore are particularly vulnerable to pollution by potentially toxic elements (PTEs). Such PTEs (see Martínez-Colón et al., 2009 for definition and further discussion) can have detrimental effects on water quality, aquatic ecosystems (i.e., reducing abundance and diversity, etc.), and human

health (e.g., Laboy-Nieves, 2009). In northern Puerto Rico, Torrecillas Lagoon (TL) has been extensively altered by anthropogenic activities (Figs. 1 and 2). From PreColombian times to present, human settlements, agriculture, deforestation, landfills, dredging and urban development have affected this extensive lagoon system (Ellis, 1976; Seguinot-Barbosa, 1983). During the late 1800s, sugar cane was grown around TL (Wilson, 1899). At present, TL is influenced by a wide range of point and nonpoint sources of pollution (Table 1), coupled with localized anoxic conditions within dredged navigational channels. Previous studies have reported that organic pollutants (PCBs, Dieldrin, DDT), as well as elevated concentrations of PTEs (As, Se, Cu, Hg, Cd Ni, Zn, and Pb) in sediments of TL are anthropogenic (Martínez-Colón and Hallock, 2010; San Juan Bay Estuary, 2000;

Abbreviations: PTE, Potentially toxic element; F2Tess-bioavailable, Carbonate bioavailable fraction from Tessier et al. (1979) ⁎ Corresponding author. E-mail address: michael.martinez@famu.edu (M. Martínez-Colón). http://dx.doi.org/10.1016/j.ecolind.2017.10.045 Received 4 June 2017; Received in revised form 21 August 2017; Accepted 20 October 2017 1470-160X/ © 2017 Elsevier Ltd. All rights reserved.