Potential effects of sediment contaminants on diatom assemblages in coastal lagoons of New Jersey and New York States

Highlights

• A correlation between diatom assemblage composition and contaminants was found.

• Abundance of small centric diatoms in surface sediments increased with pollution.

• Most benthic diatoms declined with pollution, but a few benefitted from it.

• Planktonic diatoms are getting more abundant with time.

Abstract

Sediment samples from the coastal lagoons and estuaries of New York and New Jersey were used to investigate the influence of contaminants on diatom assemblages. Multivariate analyses demonstrated correspondence between composition of diatom assemblages and concentrations of several metals and total PAH. The effects of the individual contaminants were difficult to disentangle because of the considerable correlations between their concentrations. The most conspicuous trend was the increase in the relative abundance of small centric planktonic diatoms in response to contamination and the corresponding decrease in the benthic flora. The high relative abundance of planktonic species on contaminated sediments apparently resulted not so much from their tolerance to pollution, but from the paucity of benthic species. A comparison of the assemblages on the surface and at the depth of approximately 8–10 cm revealed a statistically significant temporal change in community composition towards planktonic diatoms.

Introduction

Diatoms are commonly used as indicators of various environmental characteristics, especially salinity, pH, and nutrients (Smol and Stoermer, 2010). Diatoms are also known to be sensitive to toxic substances, such as metals (Cattaneo et al., 2008, Duong et al., 2008, Morin et al., 2012) and organic contaminants (Moisset et al., 2015). Classic toxicological approaches, such as testing the effects of contaminants on single species or monoclonal cultures in the laboratory conditions demonstrated effects of individual contaminants and of their mixtures on both freshwater (e.g., Adams and Stauber, 2004, Araújo et al., 2010, Larras et al., 2012,) and marine (e.g., Fan and Reinfelder, 2003, Hagenbuch and Pinckney, 2012, Joux-Arab et al., 2000, Moreno-Garrido et al., 2003, Moreno-Garrido et al., 2007) diatoms. While the traditional tests typically measured growth or survival rates of various species depending on the dosage and length of the exposure to contaminants, a number of recent studies attempted to investigate mechanisms of toxicity by estimating gene expression (Kim Tiam et al., 2012, Moisset et al., 2015) and enzyme activities indicating which cell functions are affected (Bonet et al., 2012, Crespo et al., 2013). Laboratory and field experiments were also crucial for investigating effects of contaminants on the composition (Morin et al., 2010, Ricart et al., 2010) and diversity (Ricciardi et al., 2009) of algal communities and the function of the river biofilm ecosystems (Barral-Fraga et al., 2015). Several researchers used mesocosms and artificial streams to study freshwater diatom community composition changes in response to contaminant exposure (Pérès et al., 1997; Kim Tiam et al., 2015). Ivorra et al. (1999) and Morin et al. (2014) documented the effect of zinc exposure on lotic diatom communities using in situ translocation experiments. While experimental work is indispensable for establishing causal relationships between pollutants and organisms, field surveys are important for detecting potential effects of contaminants on whole communities in situ and for observing the ecosystem-level effects. Cattaneo et al., 2004, Cattaneo et al., 2008 showed how diatom community composition changed with time as a result of metal pollution in several Canadian lakes with sensitive planktonic species declining in abundance and more tolerant benthic species surviving heavy pollution. Medley and Clements (1998) combined field observations with experiments to study the effects of metals on diatom community composition in Colorado streams and determined which diatom species were either sensitive or tolerant to various metals. The effects of contaminants on the species composition and diversity of benthic algae including diatoms were demonstrated in field studies of rivers in Spain (Sabater, 2000, Guasch et al., 2009, Brix et al., 2012) and in Northern Canada (Spencer et al., 2008). In comparison to freshwaters, relatively little is known about patterns of benthic diatom distribution in relation to sediment contaminants in marine environment. The effects of hydrocarbons and metals on subtidal sediment diatom assemblages were studied in Antarctica using field survey (Cunningham et al., 2005) as well as field experiments (Cunningham et al., 2003). In the temperate zone no field studies of subtidal diatom assemblages along gradients of contaminants have been done yet.

The present investigation is an attempt to reveal potential effects of contaminants on diatoms in surface sediments in the coastal waters of New York and New Jersey. This investigation is part of a survey aimed at assessing the presence of sediment contaminants after Hurricane Sandy and their effects on biota conducted by USGS in 2013. Unfortunately, no baseline data on spatial and temporal variation of surface sediment diatom assemblages in the area was available. The closest location where diatoms from sediment core samples have been analyzed was conducted in Long Island Sound (Cooper et al., 2010, Varekamp et al., 2010). An increase of planktonic to benthic diatom ratio and a decrease in species diversity and abundance of diatoms starting from 1850s were reported, but detailed data on species composition in Long Island Sound samples have yet to be published. Our study is thus the first report on the patterns of distribution of subtidal sediment diatoms in the near-shore locations of New York and New Jersey and their possible links to contaminants.