BOTTOM COMMUNITIES OF THE GULF OF MEXICO 



By Joel W. Hedgpeth, University of California 



The study of bottom communities, according 

 to the quantitative approach of Petersen, has not 

 been attempted in the Gulf of Mexico or its 

 coastal bays. It is possible to assemble informa- 

 tion, in a general way, about certain character- 

 istic bottom aggregations such as coral reefs, 

 sponge groimds, and oyster beds, but the neces- 

 sary data for comparing these areas with similar 

 situations elsewhere do not exist. This gap in 

 our knowledge has been due in part to our frag- 

 mentary information concerning the qualitative 

 composition of the flora and fauna of the area. 

 As many of the contributors of the sections on 

 various animal groups in this volume have shown, 

 our knowledge of the fauna is still far from satis- 

 factory. It is, on the other hand, not without 

 advantage that we have lagged behind other 

 countries in quantitative bottom studies, since 

 we may profit by example. Leaders in this field 

 in recent years have been Russian fishery biolo- 

 gists whose work on biological productivity, bio- 

 mass, and bottom communities in general has 

 been summarized up to 1947 by Zenkevich (1947). 

 Discussion of the methods and principles of this 

 work are available in English (Brotskaja and 

 Zenkevich, 1939; Zenkevich and Brotzky, 19.39). 

 It must be pointed out that such concepts of 

 "productivity," "production," and "biomass" 

 should be used with caution and only after careful 

 consideration of the life spans and metabolic rates 

 of the components of the community. 



An example of a study of sponge grounds, in 

 some ways comparable to those off western Flor- 

 ida, will be found in the paper by Chambost 

 (1928). Communities of bay bottoms, including 

 many closely related species living under similar 

 conditions to those encountered along the north- 

 ern Gulf coast, have been recently described by 

 de Oliveira (1948, 1950). The literature on North 

 Atlantic bottom communities has been reviewed 

 by Jones (1950) who also discusses the concept of 

 marine communities in general. 



There is a certain amount of published misin- 

 formation, most of it well intentioned, concerning 

 the occurrence of organisms which are considered 

 important community dominants in the Gulf of 

 Mexico. Andree (1920, v. 2, pi. 7), for example, 

 presents a map indicating the occurrence of pearl 

 oysters from Panama northward to Texas and 

 eastward to Alabama. Literally, this is true; 

 small specimens of Pinctada are frequently cast 

 adrift on sargassum and reach these coasis, but 

 there are no pearling grounds in the northern 

 Gulf. At the same time, however, reef building 

 oysters are not indicated west of the Atlantic side 

 of Florida, and there is no indication of the Gulf 

 of Mexico sponge grounds. This is comparable to 

 the gaps in Bartholomew's (1911) Atlas of Zoo- 

 geography and Orton's (1937) peculiar omission 

 of oysters from the northern Gulf coast. The 

 well-known map of coral reefs indicating reefs 

 throughout the Gulf prepared many years ago by 

 Joubin has appeared in many texts (including the 

 standard Russian text on hydrography). From 

 such information as this, Ekman (1935) originally 

 classified the northern Gulf of Mexico as a tropical 

 littoral region. In his new edition Ekman (1953) 

 gives a more precise account, characterizing the 

 northern part of the Gulf of Mexico as a "warm 

 temperate" region, with species common to tem- 

 perate eastern North America. A more detailed 

 discussion of the biogeographical relationships of 

 the northern Gulf of Mexico will be found in 

 Hedgpeth (1953). 



Of the various bottom communities in the Gulf 

 of Mexico, several of them of prime economic 

 importance, the most intensive work has been 

 done on the oyster bottoms. Various surveys 

 have been undertaken, mostly with the purpose 

 of delineating the beds and determining the 

 causes of decline. Wliile most of the published 

 surveys are out of date, they are useful in study- 

 ing the changes, many of them the result of human 

 interference with the environment, which have 



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