Applied Wetlands Ecology

Benthic- Macro-Invertebrate Communities and Habitat Characteristics of Created and Natural Salt Marshes in Galveston Bay, Texas

Melissa M. Romigh, Rachel E. Butzler, Bruce Simons, Stephen E. Davis, III

We evaluated the benthic macro-invertebrate community assemblages and habitat characteristics of two created and two natural salt marshes in Galveston Bay, Texas. We collected samples along replicate transects encompassing marsh interior—marsh edge—open water microhabitats to determine (1) within-marsh variability of invertebrate communities, and (2) differences in invertebrate abundance and diversity among created and adjacent natural marsh systems. In both marsh types, % OM of soil was highest in the interior microhabitat (55-73%), lowest in the open water (33-51%), and highest overall in the created marshes. The natural marshes supported 77% of the total invertebrates collected, representing 22 of the 31 total species identified. Although the created marshes supported a lower proportion, we found a greater number of species (27 species) in these marshes. Overall, the marsh edge supported the highest density of individuals (15738±5978 m-2) and species (21) of the three microhabitats. The interior and open water microhabitats were equivalent in species richness, but the open water sites were least dense (3399±950 m-2). Detrended and Canonical Correspondence Analyses were used to correlate specific site, macro-invertebrate community structure, and environmental characteristics. DCA grouped microhabitats of the older created marsh (11 yr) close to its adjacent natural marsh, suggesting a similarity in structure/function. The younger created marsh (2 yr) sites were isolated from one other and from an adjacent natural marsh. Our preliminary findings indicate that this approach is useful in detecting both intra- and inter-marsh variability in benthic community structure, and may assist in comparing and assessing wetland function.

Ecological Assessment of Created Wetlands at Big Brown Mine

Tyson Hart and Stephen E. Davis, III

Declines in wetland area and resulting changes in ecosystem properties have led to mitigation-requiring policies such as “No Net Loss”. These types of policies have sparked an increase in the number of wetland restoration and creation projects, and have revealed the need for robust indicators of mitigation success. Unfortunately, there are few comprehensive, yet detailed, studies of created wetlands in the United States. A primary goal in creating and restoring wetlands is to mimic natural wetlands both structurally (e.g., species composition, soil characteristics, hydroperiod, etc.) and functionally (e.g., primary productivity, soil respiration, nutrient uptake, etc.). In order to accomplish both, understanding the path of ecosystem development in these created or restored wetlands is needed. I propose to perform comprehensive and detailed studies of created wetlands at TXU’s Big Brown Mine. I plan to use the findings of this study to evaluate the development (i.e., maturation) of created wetlands and establish criteria for the identification of mature wetland status at Big Brown Mine. To reach this goal, I will: (1) measure various surface water/soil/vegetative characteristics in select (3 newly created, 3 intermediately mature, and 3 mature) wetlands at Big Brown Mine on a quarterly basis, and (2) describe relationships among variables and develop a set of robust indicators that best correlate with wetland maturity. The product of this research will be a detailed ecosystem-level description of created wetlands at Big Brown Mine. My findings also will contribute to the development of an index to be used in the identification of mature wetlands and the subsequent release of these lands to the private sector.

Fish and invertebrate assemblage structure in natural and constructed wetlands of the Aransas National Wildlife Refuge, Texas

Steven Zeug, Virginia Shervette, David Hoeinghaus, Stephen Davis and Rachel Butzler

In response to the loss of natural Spartina marsh habitats in Texas estuaries, efforts have been made to create new marsh habitats on dredge spoils and eroding shorelines.  The evaluation of functional equivalency is complicated by geographic location, created marsh age and evaluation criteria.  In Texas, the majority of information concerning created marsh habitat comes from studies conducted in the Galveston Bay system.  In this study we evaluate the functional equivalence of natural and created marsh habitats in the Aransas National Wildlife Refuge (wintering grounds for the last naturally migrating population of endangered whooping cranes).  We are comparing seasonal patterns in habitat characteristics, fish and invertebrate assemblage structure, body size and growth and predation by large-bodied fishes in paired natural and created Spartina marsh habitats.  This study will provide information on an understudied region of the Texas coast and aid in planning and evaluation of marsh restoration activities.  Additionally, conclusions drawn from this work have direct applications to management of marsh sites in the refuge with respect to production of whooping crane food resources (crabs and shrimp).