Marine Plants of the Texas Coast

IV. Common Seaweeds of the Texas Coast

Common Seaweeds of theTexas Coast IV Seaweeds common to theTexas coast. 85 Introduction to Seaweeds People have named and classified plants (and animals) for thousands of years. in early systems, taxonomists constructed classification schemes that recognized the similarity of groups and gathered them into clusters of natural assemblages. as science advanced, newer phylogenetic classification schemes have been developed and employed. These modern systems work very well for many organisms; however, the algae (seaweeds) are separated from other groups as a dissimilar group. newer Dna techniques have brought much information to aid in the classification of the algae but require advanced knowledge of techniques and expensive equipment. students and individuals who are identifying seaweeds in the field and in a basic laboratory need a method of identification that is reliable yet does not require advanced training and equipment. along with the keys are images that will provide visual clues to the differences between the various plants. The taxonomic names and arrangement follow Michael J. Wynne’s Checklist of Benthic Marine Algae of the Coast of Texas (2009). The species covered herein do not include rare or minute species or those found only offshore in the Gulf of Mexico (especially flower Gardens, a national marine sanctuary). also, it is important to note that with the exception of a few seaweeds, there are practically no common names used to describe the species, so scientific names are used. The seaweed (algal) body lacks differentiation into root, stems, and leaves, which separates them from angiosperms (flowering plants). The algae are all photosynthetic plants with chlorophyll a and accessory pigments. The organs associated with sexual reproduction and the sporangia are frequently unicellular and, when multicellular, all cells are fertile. The zygotes (fertilized eggs) never develop into multicellular embryos while in the female reproductive organs. This technical definition distinguishes algae from the fungi and angiosperms . The earliest attempts at subdividing the algae were based on plant color, and three main groups were recognized: red (rhodophyta), brown (Phaeophyceae ), and green (Chlorophyta). The rhodophyta are the most primitive group of seaweeds, and the Chlorophyta, the most advanced. Present-day identification of the classes is similarly based on differences of color, but using spectrophotometric and chromatographic analysis of the pigments is more accurate than visual examination. The use of these tools has enabled a more precise description of plants. Color differences are due to a predominance of one or another pigment, especially within the brown and red algae. additional support for separation of the three major groups is based on the different storage reserve products present. a point particularly appropriate to studies on the intertidal algae is that under certain environmental conditions the 86 PA r T I V predominating pigment may be lost, and red or brown seaweeds may become green in color. The marine macroalgae (seaweeds) are found in all coastal ecosystems, including rocky seashores as well as human-made jetties, salt marshes, seagrass meadows and lagoons, unvegetated bottoms of sand and mud, and, in tropical areas, coral reefs and mangrove communities. in general, the shores of the texas coast are a soft and sandy or muddy bottom where seaweeds do not grow well. The texas coast is bordered by barrier islands that essentially are large sandbars with shallow bays and lagoons that separate them from the mainland. a typical beach on the Gulf of Mexico side of the barrier island is very dynamic. The shifting sand and scouring action will usually prevent algal attachment or may bury any algae that successfully attach. Most seaweed requires some hard or solid surface for attachment. The greatest algal diversity and coverage are found attached to the artificial granite jetties associated with dredged channels of major passes. These provide water movement and tidal exchange from the estuaries out into the Gulf of Mexico, and vice versa (e.g., Galveston, Port aransas, Port Mansfield, Brazos santiago Pass). The typical rocky shoreline may be divided into three vertical regions. The intertidal (littoral) zone is exposed during low water and submerged at high water. along the texas coast, this vertical distance is usually less than 3 feet (1 m), as the tides are considered to be mixed. above the intertidal zone is the supralittoral or spray zone. The organisms living here rely on the moisture from the spray of wave action. Below the intertidal zone is the sublittoral zone, where the organisms remain submerged. note that intertidal boundaries are not fixed elevations...