Effects of herbivores and competing primary producers on Vallisneria americana in Kings Bay: implications for restoration and management

Metadata Updated: December 11, 2019

The Crystal River is an 11-km long, spring-fed river that originates in the City of Crystal River in Citrus County and discharges directly into the Gulf of Mexico. At its origin, at least 30 freshwater springs deliver a combined discharge of 26 m3 f1 into a large, approximately 1.8 km2, open area called Kings Bay. The Kings Bay/Crystal River system is a focal area for recreational activities within the region and attracts, on average, greater than 70,000 visitors per year. As is true of many aquatic systems, however, Kings Bay has been subject to increased nutrient inputs as a consequence of anthropogenic activities within its watershed and accumulating evidence suggests that water clarity and the abundance of native submersed aquatic vegetation, Vallisneria americana in particular, has declined relative to historical conditions. Moreover, nuisance species such as Lyngbya spp., Hydrilla verticillata and Myriophyllum spicatum are often more prevalent in Kings Bay thus further compromising the ecological integrity and aesthetic value of this system. The present goal of water resource managers is to reverse these changes and to restore the Kings Bay/Crystal River system to a more "healthy" state. To facilitate the restoration efforts of the Southwest Florida Water Management District, we conducted a series of field investigations designed to assess the potential effects of herbivores and competing primary producers on transplanted Vallisneria. In light of the results from these studies and with additional data collected during the course of the project, we employed a size ­specific demographic approach to address a fundamental management question specific to Kings Bay, i.e. how much Vallisneria would need to be transplanted to satisfy the energetic demand of manatees and still allow for an increase in plant biomass? Findings from our work are presented as four stand-alone chapters of this report. Results are summarized below in brief with special attention paid to their management implications. To determine the effects of herbivores and other primary producers on Vallisneria transplants, we conducted a 2 x 2 factorial design experiment at three sites (Cedar Cove, south of Buzzards Island and north of Parkers Island) in which we allowed or denied: (I) relatively large herbivores (e.g., manatees, turtles, waterfowl, large fishes) and (2) other primary producers (e.g., Myriophyllum, Hydrilla, Lyngbya) access to I .5 x 1.5 m transplanted plots of Vallisneria. Within one month, Val/isneria disappeared from 80% of herbivore-access plots due to consumption by manatees. Vallisneria density was reduced a variable amount (0-50%) in response to competitors, due to site-specific variation in natural abundance of other primary producers (at two sites - Buzzard Island and Parker Island, we observed extensive colonization by other primary producers and a strong treatment effect). Most of this competitive effect was attributable to Eurasian watermilfoil (Myriophyl/um spicatum); after pooling Va/lisneria density data across sites, we observed a negative exponential relationship between shoot density of Vallisneria and stem density of Myriophyl/um for every sampling date. We observed variable recruitment of Vallisneria transplants into larger size classes among sites, but not between treatments, and, large, established plants of Vallisneria grew at similar rates whether in a monospecific or mixed stand of macrophytes, with evidence for reduced growth in dense stands (via self-shading). Hence, a probable mechanism by which Myriophyllum reduces Vallisneria occurs via space limitation, and reduction in Vallisneria densities and/or recruitment and growth of new, young shoots. We conclude from this study, that Cedar Cove might be a possible site in which to initiate a small-scale restoration project (because of the limited effect of competitors at this site alone), but only if plants were protected from herbivores.

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References

https://ecos.fws.gov/ServCat/Reference/Profile/110608

Dates

Metadata Created Date December 11, 2019
Metadata Updated Date December 11, 2019

Metadata Source

Harvested from DOI CKAN Harvest Source

Additional Metadata

Resource Type Dataset
Metadata Created Date December 11, 2019
Metadata Updated Date December 11, 2019
Publisher Fish and Wildlife Service
Unique Identifier FWS_ServCat_110608
Maintainer
Brent Frakes
Maintainer Email
Public Access Level restricted public
Bureau Code 010:18
Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
Metadata Catalog ID C:\Program Files (x86)\FWS\DataStore\Application\OpenData\FWS_ServCat_v1_1.json
Schema Version https://project-open-data.cio.gov/v1.1/schema
Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
Harvest Object Id 357f3c79-f369-446d-939b-bdd4221884e5
Harvest Source Id 34ce571b-cb98-4e0b-979f-30f9ecc452c5
Harvest Source Title DOI CKAN Harvest Source
Data First Published 2003-06-01
Homepage URL https://ecos.fws.gov/ServCat/Reference/Profile/110608
Data Last Modified 2003-06-01
Program Code 010:094, 010:028
Related Documents "https://ecos.fws.gov/ServCat/Reference/Profile/110608"
Rights The information resource is proprietary and/or copyrighted. Access to this information by the public is very limited. Please contact the associated Point of Contact regarding additional use constraints and requirements for obtaining the information.
Source Datajson Identifier true
Source Hash e40bdcd13d4116270c9190fdcc6a31132287608b
Source Schema Version 1.1
Category "Unpublished Report"

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