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Establishing baseline seagrass parameters in a small estuarine bay
Wilzbach, M.; Cummins, K.W.; Rojas, L.M.; Rudershausen, P.J.; Locascio, J. (2000). Establishing baseline seagrass parameters in a small estuarine bay, in: Bortone, S.A. (Ed.) Seagrasses: monitoring, ecology, physiology, and management. pp. 125-135
In: Bortone, S.A. (Ed.) (2000). Seagrasses: monitoring, ecology, physiology, and management. CRC Marine Science Series, 16. CRC Press: Boca Raton. ISBN 0-8493-2045-3. 318 pp., more
In: Kennish, M.J.; Lutz, P.L. (Ed.) CRC Marine Science Series., more

Available in Authors 
    VLIZ: Botany [8759]

Keyword
    Marine

Authors  Top 
  • Wilzbach, M.
  • Cummins, K.W.
  • Rojas, L.M.
  • Rudershausen, P.J.
  • Locascio, J.

Abstract
    Baseline seagrass parameters were established in autumn-winter 1998 for a small estuarine bay, Tarpon Bay, in the J.N. "Ding" Darling National Wildlife Refuge of Sanibel Island, Florida. Distribution, abundance, and condition of the seagrasses were estimated using the transect method protocol adopted by the Southwest Florida Water Management District's Surface Water Management Program. Above-sediment biomass was estimated by weighing clipped plants. The 23 transects, varying in length from 9 to 200 rn, involved the sampling of 80 l-m2 quadrats that contained one or more of the three seagrass species present in Tarpon Bay, turtle grass (Thalassia testudinum), shoal grass (Halodule wrightii),and manatee grass (Syringodiumfiliforme). The seagrasses were evaluated for Blaun-Blanquet cover classes and mean blade length in each m2 quadrat along with the number of short shoots of each species that were enumerated in three 100-cm2 frames placed within the quadrat. Length-mass regressions were independently developed to allow conversion of short-shoot densities, together with mean blade lengths, into estimates of standing crop biomass. The calculated and directly measured estimates of grams dry mass m-2 of the three species in Tarpon Bay are in the low range of those reported in other studies (T. testudinum = 15-119, H. wrightii = 2-28, and S.filiforme = 66-105). The comparatively low estimates may be attributable to seasonal variation, differences among studies in the portion of the plant measured, variation in the presence of encrusting organisms on the seagrass blades, and the effect of variations in blade width on the calculated biomass estimates. Of the three species in Tarpon Bay,T. testudinum was most ubiquitous, occurring in 66% of the quadrats. All three species showed a preference for sand over muddy sand (the most abundant bottom type, 61% ) and sediments with coarse shell. In addition, H. wrightii exhibited a very strong affinity for mud sediments. In all Blaun Blanquet cover classes, the three species showed a gradient in depth of occurrence with H. wrightii at the shallowest depths, T. testudinum at intermediate depths, and S. filiforme in the deepest locations. Although light transrnission showed an expected negative correlation with depth, sediments were not consistently correlated with depth. This study is the initial phase in the long-term evaluation of seagrass community health in Tarpon Bay as a major reference site for the Caloosahatchee River estuary-bay system.

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