californicus, Phragmites australis, Eleocharis spp., Cyperus spp., Juncus spp., Ludwigia sp., 
Sagittaria spp. and Paspalum lividum (Table 2.3) (1, 15). Higher fresh marshes are typified by 
Spartina spartinae, Paspalum spp.. Polygonum spp., Panicum spp., Borrichia, Rhynchospora 
macrostachya, Fimbristylis sp.. Aster spp. and Sesbania drummondii. Many species of Spartina 
exhibit broad salinity tolerances and are found in several categories of marsh. Fluvial woodlands 
along floodplains cover 450 km 2 (12) and support a variety of water-tolerant trees and shrubs (Table 
2.3), including Fraxinus spp., Salix nigra, Ulmus spp., Celtis spp., Carya spp. and Quercus spp. 
Swamps containing saturated soils or nearly permanent standing water comprise 50 km 2 (12) and are 
dominated by Taxodium distichum (Table 2.3). Additional information on wetland plants is also 
available (16). 
Between wetland surveys of 1956 and 1979, several changes were noted in vegetation patterns in 
the estuary: (1) expansion of open water into former marshes and woodlands; (2) expansion of 
marshes along the bay side of barrier islands into prior tidal flats; (3) formation of wetlands farther 
up creek valleys; (4) landward expansion of existing marshes; (5) reduction of submerged vegetation; 
and (6) reduction or modification of wetlands by human activities (15). Of primary concern are the 
losses of 63 km 2 of fresh marsh and 42 km 2 of salt and brackish marshes during this period. These 
losses are ascribed to such activities as channelization, impoundments, filling and subsidence 
associated with subsurface petroleum or water extraction. 
Invertebrates 
Invertebrates within the Galveston Bay system are discussed by component groups such as zoo¬ 
plankton, benthos, and mobile and sessile macrofauna. While there have been a number of studies 
of invertebrates in this area, there are no synoptic zooplankton or macro faunal surveys on a bay-wide 
basis. 
Zooplankton—A 12-month study of zooplankton in the upper Galveston and Trinity Bay areas 
(1) revealed 70 species representing nine phyla. The most abundant plankters included copepods 
(primarily Acartia tonsa, followed by Labidocera, Cyclops and Oithoina) and barnacle nauplii 
(Balanus spp.); in fact, these two phyla plus a mixed assemblage of copepod nauplii and copepodites 
represented >70 percent of the zooplankton in 11 of 12 months. Other phyla included rotifers 
(Asplancha, Brachionus, Keratella), dinoflagellates (Noctiluca scintillans) and larvaceans 
(Oikopleura). Zooplankton densities peaked in April (dominated by copepod nauplii and Nocti¬ 
luca) and August (Acartia and copepod nauplii). Barnacle nauplii were most dense in late winter- 
early spring. Fluctuations in zooplankton densities were not linked to variations in river flow, but 
salinity regimes regulated species composition and seasonal distribution. 
A three-and-a-half-year study (17) of the larger zooplankters in the same region (mouth of the San 
Jacinto River and southern Trinity Bay) identified 94 taxa dominated by crustaceans and fishes. Crab 
larvae, tentatively identified as Rhithropanopeus harrisii, were the most abundant group followed 
by other crustaceans such as Petrolisthes armatus, Pinnixa sp., Palaemonetes spp. and Callinectes 
spp., and by the fishes Brevoortia patronus and Anchoa mitchilli. Two broad seasonal groups were 
detected relating to abundance of organisms, with a "warm" season characterized by many larval 
crustaceans and few fishes and a "cool" season where the reverse trend was found. 
A 16-month study of the zooplankton of Christmas Bay (18) indicated that this high salinity 
embayment hosted a permanent zooplankton assemblage of three species (Mnemiopsis mccradyi, 
a ctenophore, and Acartia tonsa and Oithoina colcarva, copepods) apparently unaffected by 
temperature and salinity fluctuations. Other taxa such as larval crustaceans, other copepods, and the 
ctenophore Beroe ovata exhibited summer peaks in abundance. 
No zooplankton studies have been conducted in West Bay or East Bay. 
Benthos—Six benthic macroinvertebrate assemblages occur in the Galveston Bay complex, 
including open bay center, oyster reef, grassflat, bay margin, inlet-influenced and river-influenced 
assemblages (Table 2.4). The river-influenced assemblage covers the greatest area, including all of 
Trinity Bay, upper Galveston Bay, and part of East Bay. Oyster reef assemblages occur primarily in 
central Galveston Bay and divide Galveston Bay into upper and lower sections. Lower Galveston Bay 
contains primarily inlet-influenced and open bay center assemblages. The bay margin assemblage 
occurs on thebay side of Bolivar Peninsula and near Texas City. All six assemblages are found in West 
Bay. 
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