Monitoring of Ecological Conditions

During the Gray's Reef cruise aboard NOAA Ship Nancy Foster, scientists will be collecting samples as part of a long-term monitoring effort to assess status of ecological condition and potential stressor impacts within the sanctuary with a focus on the soft-bottom benthos and sediment quality.

Conceptual view of benthic fauna at GRNMS (Photo: NOAA-NCCOS) Click here for larger view

This work is a follow-up to previous (2000, 2005) ecological characterization of the condition of benthic fauna and concentrations of chemical contaminants in sediments and biota at the Gray's Reef National Marine Sanctuary (GRNMS). Results of these earlier studies (Hyland et al. 2001, 2006; Balthis et al. 2007) suggest that the sanctuary was in 'good health' with respect to these properties, although trace concentrations of pesticides, PCBs, and PAHs were detected in both sediments and biota (albeit at low concentrations).

Station locations for 2012 surveys (Photo: NOAA-NCCOS) Click here for larger view

A recent (January 2012) GRNMS Science Advisory Group (SAG) meeting recognized the importance of an ongoing program for long-term monitoring of ecological condition within the sanctuary on a periodic basis. Accordingly, the present study was planned for July 25-29, 2012, twelve years after the original baseline survey and seven years after the first re-survey, to provide a re-evaluation of sediment quality and condition of resident benthic fauna within the sanctuary. The objective of the work was to complete the sampling of these parameters following an established sampling design and protocols, and thus to provide a means for tracking potential long-term changes in the ecological condition of the sanctuary based on these indicators in support of the GRNMS management plan (NOAA 2006) and the GRNMS Condition Report (Office of National Marine Sanctuaries, 2008). However, due to mechanical problems with the R/V Joe Ferguson, cruise activities had to be halted on July 29 after only 11 of the planned 20 stations had been sampled (Figure 1). The 11 stations sampled do not provide enough coverage of GRNMS for a complete probabilistic characterization of condition within the sanctuary. Thus, a short (~ 3 day) follow-up cruise is now scheduled June 2-4, in partnership with the GRNMS, to complete the sampling and meet the original objectives of this survey.

Benthic Grab Sampling (Photo: NOAA-NCCOS)

During both the 2000 and 2005 surveys, 20 stations were sampled throughout the sanctuary boundaries. A random sampling design was applied to support probability-based estimates of the percentage of area with degraded versus non-degraded condition relative to various measured environmental indicators. The resulting sampling framework is a 58-km2 grid of 20 individual 2.9-km2 cells, each of which contains a randomly selected station, and which together are representative of the total area of the sanctuary. With such a design, each sampling point (station) is a statistically valid probability sample.

Thus, percentages of the sanctuary with degraded vs. non-degraded environmental condition relative to selected indicators and corresponding management thresholds can be estimated based on conditions observed at individual sampling points. The percentage of overall degraded area, for example, can be computed by dividing the summed areas of individual cells in which impacts were observed by the total area of the sanctuary. Statistical confidence intervals around these estimates can be calculated as well. For the upcoming 2013 survey, the same probabilistic sampling approach will be applied, with a new random station location selected within each of the 20 cells.

Sampling parameters Click here for larger view

At each of nine stations, samples will be collected for characterization of general habitat conditions (depth, temperature, salinity, pH, DO, TOC, grain size), concentrations of sediment contaminants (metals, pesticides, PCBs, PAHs), diversity and abundance of macroinfauna (> 0.5 mm), and aesthetic quality (presence of anthropogenic debris, visible oil, noxious sediment odor, and water clarity/turbidity).

A CTD unit with a rosette sampler will be supplied by NOAA Ship Nancy Foster. This unit will be used to acquire continuous profiles of conductivity, temperature, pH, dissolved oxygen, and depth as it is lowered through the water column. The unit also will be equipped with 12 Niskin bottles to acquire discrete water samples at two designated water depths: 0.5m below sea surface, and 3-5 m off seabed.

A maximum of 12 Centropristis striata (black seabass) will be collected using hook-and-line fishing methods from a subset of stations during the sampling cruise for tissue contaminant analysis (6 black seabass were collected in 2012).

Resulting data from the 2012 and 2013 studies will be compared to earlier data from 2000 and 2005 to look for trends in the measured variables and any evidence of changes in the quality of the sanctuary condition including potential signals of anthropogenic stress. The information should help fulfill important science and management goals of the sanctuary including providing valuable support to future management plans and condition reports.