Characterization of Ambient Water Quality in Natural and Created Wetlands of the Texas Coast

Purpose/Objectives

The major objectives of this project are to 1) gather water quality data to compare created and natural marshes to open water systems in order to help create water quality standards; and 2) to determine if biotic factors are correlated to water quality data.

Study Area

Galveston Bay System, Texas

Project Period

November 2013 – November 2014

Description

The United States Environmental Protection Agency (EPA) has expressed interest in creating water quality criteria and standards specific to coastal and inland wetlands. When established, these standards would be incorporated into various agencies' decision-making processes. Environmental agencies and professionals have long recognized the fundamental difference in ambient water quality between open water systems and wetlands and the need to develop specific standards for each system. Saltwater wetlands provide a variety of ecosystem services, but little research has been done on the water quality of these marshes. Besides not knowing the annual trends in saltmarsh water quality, there have been no studies looking at water quality differences between open water, created marshes, and natural marshes. Due to large amounts of human disturbance and construction, saltmarshes have been created to comply with mitigation requirements, or restored after habitat loss. The Galveston Bay system has a large variety of both created, restored, and natural salt marshes. Previous studies both in Galveston Bay and across the country have looked at various comparisons between created and natural marshes, such as vegetation composition, benthic communities, and nekton use. This project's focus compares water quality from both natural and created marshes to nearby open water sites as well as various biotic factors of each marsh. These data will be used to determine if there is a correlation between the various biotic factors and water quality.

Five marsh sites were selected from around the Galveston Bay area. Two tidal marshes from West Bay, one tidal marsh from Galveston Bay, and a tidal and freshwater marsh from Trinity Bay. Due to the level of human impact in upper Galveston Bay, we were unable to find a natural marsh to pair with our created marsh; therefore, we paired it to the tidal marsh in Trinity Bay. Each marsh had its own open water site paired to it for comparison.

Onset HOBO data loggers were used to collect conductivity, temperature, and dissolved oxygen data for four days before water samples were collected and instantaneous readings using a YSI sonde were taken. After the in-situ samples were collected they were taken back to the lab to be analyzed for nutrient content, bacterial levels, total suspended solids, and chlorophyll-a levels.

Vegetation densities and species composition was determined for each marsh using random points and vegetation quadrates. Paired with these vegetation quadrates, benthic core samples were collected to determine the benthic community composition and density. Seining was conducted to collect nekton from each marsh. Bird use was documented using a point count method at each site when water samples were collected. These biological data will be compared to the water quality data to determine if there is a correlation between the biological data and water quality data.

The research from this project will ultimately contribute to the water quality standards determination for wetlands by the EPA and state agencies. This research will also help us better understand the relationships between the biological processes of coastal marshes and water quality. Data analysis is ongoing.

Publications and Presentations

Zarnstorff, N., Guillen, G. 2016. Characterization of ambient water quality and associated factors in natural and created wetlands of the Texas coast. Texas Academy of Science Meeting, Junction, TX. Presentation.

Zarnstorff, N., Guillen, G. 2016. Characterization of ambient water quality, soil nutrients, and biological communities in natural and created wetlands of the Texas coast. State of the Bay Symposium, Galveston, TX. Poster.

Zarnstorff, N., Guillen, G. 2015. Characterization of ambient water quality in natural and created wetlands of the Texas coast. Texas Academy of Science Meeting, San Antonio, TX. Poster.

Zarnstorff, N., Guillen, G. 2015. Characterization of ambient water quality in natural and created wetlands of the Texas coast. Texas Bays and Estuaries Meeting, Port Aransas, TX. Poster.