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- Title: Re-Occurrence of the Tropical Green Macroalga, Penicillus Capitatus (Chlorophyta: Bryopsidales), In the Lower Laguna Madre of South Texas (General Notes) (Report)
- Author : The Texas Journal of Science
- Release Date : January 01, 2007
- Genre: Engineering,Books,Professional & Technical,
- Pages : * pages
- Size : 198 KB
Description
The siphonaceous green alga Penicillus capitatus Lamarck is a common macroalga of the Carribean and Gulf of Mexico (Littler & Littler 2000). This shaving brush-shaped macroalga was a common inhabitant of the Lower Laguna Madre, Texas (LLM) until about 40 years ago when the population was decimated following a salinity decline in the fall of 1959, another salinity reduction due to Hurricane Carla in 1961, and finally a severe freeze in 1962 (Sorensen 1963). Since that time, there have been no reports of P. capitatus in the LLM. During a reconnaissance trip in July 2006, a small population was found in the southern portion of the LLM. The species descriptions by Taylor (1960) and Sorensen (1979) were used in the identification of specimens. Herbarium specimens have been deposited in the herbaria of The University of Texas-Pan American Coastal Studies Laboratory (accession number C012), and the University of Texas at Austin Marine Science Institute. Penicillus capitatus thalli were mostly concentrated on unvegetated, unconsolidated sediment, colloquially termed "potholes" or "blowouts", surrounded by the seagrass Thalassia testudinum in the LLM (26[degrees] 08' 48.7" N, 097[degrees] 11' 52.0" W), approximately 7.1 km north of the Brazos-Santiago Pass. Other macroalgae found with P. capitatus were Caulerpa mexicana Sonder ex. Kutzing and C. prolifera F. obovata (Forsskal) Lamouroux. Halimeda incrassata, Caulerpa prolifera, and Codium taylorii were noted as recent colonizers to the Laguna Madre (Kaldy 1996; DeYoe & Hockaday 2001). Penicillus capitatus, C. prolifera, and C. mexicana were found growing in monotypic stands in an area of the LLM characterized by clear, nutrient-poor water 1.2 to 1.3 m deep (Kaldy & Dunton 1997; Kaldy et al. 2004). Salinity during the July 2006 trip was 37 PSU and water temperature was 31[degrees] C. The general area was surveyed and many of these potholes were recently vegetated by T. testudinum deduced from a rugose appearance of the potholes (caused by dead bundle sheaths) and the presence of dead rhizome material in the sediment. Many of these pothole P. capitatus plants were found with their holdfasts attached to the bundle sheath material. On this trip P. capitatus biomass samples were collected in three 9 cm diameter cores (0.006 [m.sup.2]) driven 10 cm into the seabed. Sediment was washed from the samples through a 1 mm mesh sieve immediately upon return to the lab and stored in sealed plastic bags and refrigerated until processed. Processed samples were dried at 80[degrees]C to a constant dry weight and weighed to the nearest 0.001 g, then ashed in a muffle furnace at 500[degrees]C and reweighed to the nearest 0.001 g. Mean biomass (dry weight) for P. capitatus was 158.03 g [m.sup.-2] (SE = 11.53 g [m.sup.-2]) and AFDW 54.47 g [m.sup.-2] (SE = 5.78 g [m.sup.-2]). Sorensen (1963) reported a mean dry weight of 5.14 g per 4 inch (10.16 cm) diameter core which is equivalent to 634 g [m.sup.-2].