Health and resilience of salt marshes in Jamaica Bay, NY: Geochemical and dynamical perspectives

Cochran, J.; Zhu, Qingzhi; Heilbrun, Christina; Tamborski, Joseph; Yin, Hang; Fitzgerald, Parick; Perez-Tuero, Jorge; Feng, Huan

Jamaica Bay is a highly urbanized estuary (~80 km2) located between the boroughs of Queens and Brooklyn in New York City, NY (USA), with a connection to the Atlantic Ocean through Rockaway Inlet (Fig. 1.1). There are over a dozen isolated marsh islands within Jamaica Bay, some of which are natural, and many of which have been restored through engineering efforts. Four primary sewage treatment plants discharge over 300 million gallons of treated effluent into Jamaica Bay per day, which carry significant loads of dissolved nutrients and trace metals (Benotti et al., 2006). Eutrophication in Jamaica Bay, from sewage treatment plant effluent and combined sewer overflows, is thought to be an important driver of salt marsh degradation and loss, with reduced sediment loads, dredging, boat traffic, and an increase in sea level acting as additional factors (Hartig et al., 2002). Degradation has increased in recent years to an estimated 134 km/yr of creek and open-bay-edge marsh loss, corresponding with an increase in N loads (Hartig et al., 2002). Microbial respiration of organic matter in the water column leads to significantly low levels of dissolved oxygen, which subsequently results in coastal acidification within the bay (Wallace et al., 2014). Inputs of submarine groundwater discharge to Jamaica Bay are (0.8 – 9.0) *109 L d-1, estimated from a radium (Ra) isotope mass balance, with the majority of the flow composed of recirculated seawater (Beck et al., 2007). The large volumetric contribution of recirculated seawater through the coastal aquifer is a minor source of nutrients but a significant source of dissolved trace metals, with the flux of Fe, Zn, Co and Ni rivalling inputs from treated wastewater effluent (Beck et al., 2009). The high input of nutrients and metals from these various point-source and nonpoint-sources have resulted in significant environmental degradation and loss to the Jamaica Bay salt marsh ecosystem. This report presents the results of a systematic study of salt marshes in Jamaica Bay over a two-year period from 2014 to 2016 (Fig. 1.1). The marshes studied – Big Egg, Elders Point East and West and JoCo – were selected because they spanned the range from fully restored marshes (Elders East in 2006/07, and Elders West in 2010), to partially restored (Big Egg in 2003), and to a natural marsh considered ‘healthy’ (JoCo). Three sampling sites were established in each marsh (see the Google Earth maps of sampling sites in Supplementary Information of Part 2 of this report). These sites were selected in part to complement those sampled in an earlier study (Cochran et al., 2013) and in part to coordinate with ongoing research such as accretion rates determined via Surface Elevation Tables (SETs). Pore water samples were collected at two times of the year, (spring and late summer/early fall) using “sippers” and push-point piezometers that collected water from discrete depths. These were supplemented with chemical sensors sensitive to the concentrations of H2S and Fe2+ in pore water. The latter produced two-dimensional images of sulfide and iron concentrations in the upper 25 cm of the marsh peat (e.g. Fig. 1.6). Sediment cores were collected for solid phase geochemistry and for accretion rate determination (at Big Egg and JoCo) using the natural radionuclide 210Pb. Larger volume pore water samples were analyzed for the natural radionuclide 224Ra to determine drainage rates of water through the marsh peat. Details of the sampling site locations, pore water and solid phase geochemistry, and accretion and drainage rates of the marshes studied are presented in Parts 2-4 of this report.

Health and resilience of salt marshes in Jamaica Bay, NY: Geochemical and dynamical perspectives

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