Success criteria and adaptive management for a large-scale wetland restoration project

173

We conducted a study to determine the trophic pathways leading to juvenile fish in 2 mesohaline tidal marshes bordering Delaware Bay. The relative roles of the major primary producers in supplying energy, ultimately, to the mummichog Fundulus heteroclitus were assessed by measuring the stable isotopic compositions of juveniles (21 to 56 mm total length, TL; most of which were young-of-the-year) and those of macrophyte vegetation, phytoplankton, and benthlc microalgae at each site. We collected samples of primary producers and F. heteroclitus, the dominant fish species in this and other marshes along the east coast of the USA, in June and August 1997, at 2 study sites (upstream and downstream) within Mad Horse Creek (a Spartina alterniflora-dominated site) and Alloway Creek (a Phragmites australis-dominated site), for a total of 4 study sites. Our results indicate that F. heteroclitus production is based on a mixture of primary producers, but the mixture depends on the relative abundance of macrophytes. In S. alterniflora-dominated marshes, C and S isotope ratios indicate that F. heteroclitus production is supported by S. alterniflora production (ca 39%, presumably via detritus), whde in P. australis-dominated marshes, secondary production is based upon P. australis (73%). To our knowledge, this finding provides the first evidence that P. australis may contribute to aquatic food webs in tidal marshes. Benthic microalgae also contribute to the food chain that leads to E heteroclitus in both marsh types, while phytoplankton may be of lesser importance. Benthic microalgal biomass was lower in the P. australis-dominated system, consistent with a greater effect of shading in P. australis-versus S. alterniflora-based creek systems. Based on the difference in nitrogen isotope values between F. heteroclitus and the primary producers, the trophic level of E heteroclitus appears to be similar in the 2 marsh types, despite the differing vegetation types. In summary, the relative roles of the primary producers in supplying energy to F. heteroclitus varies locally and, in particular, with respect to the type of marsh macrophyte vegetation.

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Relative importance of benthic microalgae, phytoplankton and the detritus of smooth cordgrass Spartina alterniflora and the common reed Phragmites australis to brackish-marsh food webs

Wainright¹,

Weinstein²,

Able³

et al. 2000

173

“…These sites ranged from the poly/mesohaline lower bay (mean salinity 12 to 20) to the oligo/mesohaline upper bay (0 to 12) and have been described in detail in Able et al (2000Able et al ( , 2001. Of the sampling sites, 3 were undergoing or had undergone restoration as part of the Public Service Enterprise Group's Estuary Enhancement Program during (or prior to) this study (Weinstein et al 1997). The 2 sites closest to the ocean, Dennis Township and Moores Beach, are close to each other and have similar physico-chemical conditions and fish faunas (Able et al 2000).…”

Section: Methodsmentioning

confidence: 99%

Spatial patterns in diet and distribution of juveniles of four fish species in Delaware Bay marsh creeks: factors influencing fish abundance

Nemerson¹,

Able²

2004

Delaware Bay is one of the largest estuaries on the east coast of the United States and provides juvenile habitat for many fish species. We investigated spatial patterns in the diet and distribution of the young-of-the-year of 3 marine transients -the weakfish Cynoscion regalis, the spot Leiostomus xanthurus and the Atlantic croaker Micropogonias undulatus -and the juveniles and adults of 1 estuarine resident, the white perch Morone americana, in 5 marsh creeks systems along a salinity gradient running from the poly/mesohaline (12 to 20) lower bay to the meso/oligohaline upper bay (0 to 12). Sampling was conducted monthly from April through November in 1997 and 1998, resulting in over 1700 otter trawl (4.9 m, 6 mm cod-end mesh) samples and 5703 fish stomachs examined, making this one of the largest studies of its kind. We employed a bootstrap technique to generate 95% confidence intervals for proportional consumption of the major prey categories. The diets of the target species differed significantly among the 5 marsh creeks. Mysid consumption was high for all species at the 3 most saline marshes and low at the 2 freshest sites, suggesting either low mysid abundance or availability at the latter sites. Consumption of insect larvae was important only at the freshest site. L. xanthurus consumed 80% annelids at the most saline sites, but less that 32% at the other sites. The other important consumer of annelids, Micropogonias undulatus, consumed similar quantities of annelids at all sites (32 to 41%). Total stomach fullness was almost always higher at the sites of highest fish abundance. We conclude that the marine transients appear to recruit preferentially to sites of high resource abundance, while M. americana is restricted by physico-chemical tolerance during the spring through fall to limited juvenile habitats where it may experience food resource competition.

“…Control of water levels would be more efficient within impoundments of smaller size or with better drainage capability. Alternative methods of marsh management should also be explored (Weinstein et al 1997, Turner & Streever 2002.…”

Section: Management Implicationsmentioning

confidence: 99%

Hydrologic aspects of marsh ponds during winter on the Gulf Coast Chenier Plain, USA: effects of structural marsh management

Bolduc¹,

Afton²

2004

The hydrology of marsh ponds influences aquatic invertebrate and waterbird communities. Hydrologic variables in marsh ponds of the Gulf Coast Chenier Plain are potentially affected by structural marsh management (SMM: levees, water control structures and impoundments) that has been implemented since the 1950s. Assuming that SMM restricts tidal flows and drainage of rainwater, we predicted that SMM would increase water depth, and concomitantly decrease salinity and transparency in impounded marsh ponds. We also predicted that SMM would increase seasonal variability in water depth in impounded marsh ponds because of the potential incapacity of water control structures to cope with large flooding events. In addition, we predicted that SMM would decrease spatial variability in water depth. Finally, we predicted that ponds of impounded freshwater (IF), oligohaline (IO), and mesohaline (IM) marshes would be similar in water depth, temperature, dissolved oxygen (O 2 ), and transparency. Using a priori multivariate analysis of variance (MANOVA) contrast, we tested these predictions by comparing hydrologic variables within ponds of impounded and unimpounded marshes during winters 1997-1998 to 1999-2000 on Rockefeller State Wildlife Refuge, near Grand Chenier, Louisiana. Specifically, we compared hydrologic variables (1) between IM and unimpounded mesohaline marsh ponds (UM); and (2) among IF, IO, and IM marshes ponds. As predicted, water depth was higher and salinity and O 2 were lower in IM than in UM marsh ponds. However, temperature and transparency did not differ between IM and UM marsh ponds. Water depth varied more among months in IM marsh ponds than within those of UM marshes, and variances among and within ponds were lower in IM than UM marshes. Finally, all hydrologic variables, except salinity, were similar among IF, IO, and IM marsh ponds. Hydrologic changes within marsh ponds due to SMM should (1) promote benthic invertebrate taxa that tolerate low levels of O 2 and salinity; (2) deter waterbird species that cannot cope with increased water levels; and (3) reduce waterbird species diversity by decreasing spatial variability in water depth among and within marsh ponds.