Ecology of benthonic species

Abstract

The faunal composition of zones A, D, E, and F off Central America is similar to that of equivalent zones off California; zones B and C are characterized by different species in the two regions. Zonal boundaries are at greater depths off California than off El Salvador. Physical and chemical factors that appear to influence distribution of Foraminifera are: depth; temperature, salinity, and oxygen content of the water; and nitrogen content and grain size of the bottom sediments. Salinity and oxygen values are very similar at corresponding zonal boundaries off California and off Central America. Temperature at these zonal boundaries is 5° to 10° higher in the shallow zones and 2° to 3° higher in the deep zones off Central America than off California, although the amount of seasonal variation is similar. Nitrogen values are similar in the two regions. Data on grain size are inadequate for comparison. The significance of the factors varies from zone to zone. Zone A is characterized by wide variations in temperature and salinity, and the species of this zone are those that can tolerate such wide variations. Zone B is subject to smaller seasonal variations, and its base is close to the bottom of the thermocline. It is characterized by different species off Central America than off California; water temperatures in this zone off Central America are higher than off California. Therefore species of this zone must be sensitive to the wide temperature difference between North American and Central American waters, though able to tolerate some variation in temperature and salinity. Zone C is below the thermocline and therefore subject to little seasonal temperature variation. Like zone B, it is distinguished by different species off North and Central America. Species of this zone tolerate, or may even require, cooler water and smaller seasonal variation than those of shallower zones. Zones D, E, and F are on the continental slope. Physical and chemical factors show little if any seasonal variation. Temperature decreases with increasing depth; oxygen reaches a minimum in zone D and then increases downward. Faunal differences between these zones must be controlled largely by downward decrease of temperature combined with uniform seasonal environment. Zones A, B, and C have small depth ranges; zones D, E, and F have large ones. In these latter zones, infraspecific morphologic variations have been found, with deeper water forms (more than 800 meters) tending to have well-developed costae, keels, or carinae.

Relationship of benthic foraminiferal diversity to paleoproductivity in the Neogene Caribbean

“…Although these taxa are also found at Site 999, other common Caribbean taxa (e.g., C. wuellerstorfi) do not occur at the Pacific site. Shallower tropical Eastern Pacific biofacies as described by Smith (1964) and McDougall (1985) seem no more comparable to the Caribbean Site 999 biofacies, so we have compared the general lower bathyal-abyssal biofacies from each side of the Panamanian isthmus (Fig. 1).…”

Methods

“…The generic classification of Loeblich and Tappan (1988) was used. The depth distribution of benthic foraminifers is based on recent ecological data of Bandy and Arnal (1957), Crouch and Poag (1987), Heinz et al (2008), and Smith (1963Smith ( , 1964 reported from the Pacific off Central America.…”

Benthic foraminiferal distribution and sedimentary structures suggest tectonic erosion at the Costa Rica convergent plate margin

“…Characteristic genera of these environments include Uvigerina , Bulimina , Globobulimina , Brizalina and Bolivina , which frequently occur in eutrophic and oxygen‐limited ecosystems such as oxygen minimum zones at intermediate water depths (Sen Gupta and Machain‐Castillo, 1993; Bernhard and Sen Gupta, 1999). Off Middle America the modern‐day oxygen minimum zone extends from approximately 400 to 900 m (Smith, 1964).…”

“… References: 1 Smith (1964); 2 McDougall (1985); 3 Pflum and Frerichs (1976); 4 Lutze (1980); 5 Schmiedl et al . (1997); 6 Schiebel (1992); 7 Mead (1985); 8 Bornmalm (1997); 9 Corliss (1979); 10 Ingle and Keller (1980); 11 Sen Gupta and Machain‐Castillo (1993); 12 Corliss (1985); 13 Rathburn and Corliss (1994); 14 Mackensen et al .…”