Abstract Methods Restricted Interior Environment Foraminiferal Distribution Current Transport Conclusions Acknowledgments Literature Cited Appendix

The dominant taxa examined from Florida Bay and adjacent environments are listed alphabetically below by family. Not all occur in the bay, and those mentioned that do not are nevertheless included both for comparative purposes and because they are significant constituents diagnostic of the larger platform population of which the faunal assemblages of Florida Bay are a part. Unless otherwise noted, all taxa belong to the epifauna. General habitats are given by family; limits of occurrence, controlling factors, and value as environmental indicators are discussed by species as they apply to this study only. Many of these species may occupy quite different biotopes in other areas.

(1) Alveolinidae - normal oceanic conditions (Fig. 7): Borelis pulchra (d'Orbigny), a fusiform species, occurs sporadically in margin and open interior environments. Its abundance ranges between 1 and 3% of the foraminiferal population, and it prefers depths of 1 to 15 m (Fig. 8).

(2) Amphisteginidae - high-energy conditions (Figs. 4, 7): the calcareous perforate Amphistegina "lessonii" d'Orbigny is narrowly limited to reefs and patch reefs of the outer margin and shallow slope areas. Typically composing 10 to 20% of faunas from 9- to 15-m depths along the outer reef, the species is much less abundant, or even absent, in sandy or muddy sediments immediately behind the marginal reef (Fig. 8). Reappearing landward on patch reefs, A. "lessonii" averages 5 to 6% of the fauna.

(3) Articulinidae - shallow, grass-covered backreef areas: unidentified species of the calcareous imperforate Articulina are most abundant on the margin just landward of the platform edge, where they constitute 6 to 12% of the foraminiferal population (Fig. 8). In quieter, more protected areas of the platform interior, the urn-shaped, rectilinear, compressed tests characteristic of this genus are considerably less abundant (1 to 3%, and occasionally 7%). Articulina species are not found in Florida Bay.

(4) Asterigerinidae - high-energy, hard substrate environments: Asterigerina carinata d'Orbigny, a small, sharp-edged, trochoid, calcareous perforate species, is restricted to outer parts of the carbonate platform (Fig. 8). Although this species is commonly found with other foraminifera known to prefer reef habitats, its occurrence is apparently related more to the proximity of the platform edge and oceanic waters than to reefs. It is an excellent indicator of the platform margin environment.

(5) Ataxophragmiidae - calm, restricted conditions: Clavulina tricarinata d'Orbigny, an elongate arenaceous form, occurs most often in shallow, quiet, open interior and platform margin sediments, where it commonly constitutes 6 to 9% of the foraminiferal population (Figs. 8, 9). It is found in less than a quarter of the Florida Bay sites sampled, and its abundance does not exceed 3% in any of them (Figs. 5, 6). It is not found in the western part of Florida Bay.

Valvulina oviedoiana d'Orbigny is a triserial arenaceous species occurring sporadically in coarser sediments of Florida Bay "lakes" and the open interior (Fig. 3). In the bay its abundance varies from a usual 4 to 8% to local highs of 15 to 30% (Figs. 5, 6, 9). The species does not occur in brackish areas and is not found in the western part of the bay.

(6) Discorbidae - most common on platform and margin (Fig. 2); some species common in brackish environments: Rosalina rosea (d'Orbigny), one of several trochoid, calcareous perforate species in outer shelf sediments, is a small, distinctive, pink foraminifer whose distribution (6-9% frequency), like that of other reddish or pink species, is closely related to the occurrence of reefs (Figs. 5, 8). The species is not, however, limited to reef areas and appears in frequencies of 1 to 2% in sediments from more open parts of the platform interior.

Trichohyalus aguayoi (Bermudez) is not a common or widespread foraminifer. Confined to the restricted interior environment, it shows a clear preference for extremely shallow water next to small islands (Fig. 3). It is typically found about 0.3 m deep within 15 m of shorelines of the interior mud islands of Florida Bay (Figs. 5, 6). Normally present in frequencies of 2 to 6%, it composed 18% of the population in sample #7422 (Fig. 1). Able to tolerate both elevated and lowered salinities, T. aguayoi typically does not occur in brackish areas, nor is it found near islands in the more open western part of Florida Bay. The frosted nature of the trochoid, vitreous, calcareous perforate test is compatible with hypersaline conditions.

Discorbis mira Cushman, Rosalina aff. R. floridana (Cushman), and R. suezensis (Said) occur sporadically but are present in most of the Florida carbonate realm, usually in abundances of 1 to 3% (Figs. 2, 5, 6, 9). No ecologic relationships with depth, water circulation, sediment grain size, or proximity to land are immediately apparent for these calcareous perforate species; however, frequencies of Rosalina species reach 15% on the platform margin (Fig. 8).

(7) Elphidiidae - common throughout all shallow-platform conditions (Figs. 2, 4, 7): Elphidium discoidale (d'Orbigny) occurs in greatest numbers in muddy nearshore areas and/or in water less than 1.5 m deep. This planispiral, calcareous perforate species (Figs. 2, 3) composes about 40% of the population near the Florida mainland and is also abundant on shallow Florida Bay mudbanks (Figs. 5, 6, 9), decreasing to 3-6% frequencies on the platform margin (Fig. 8). It is apparently highly tolerant of both hypersaline and brackish water, although it does not occur in brackish areas in the terrigenous sediments of the northern Gulf of Mexico (C. W. Poag, pers. comm., 1976). It is the most truly ubiquitous species encountered in the Florida carbonate province.

(8) Eponididae - not common, but found everywhere from margin to abyssal depths: Epondies antillarum (d'Orbigny) and Poroeponides lateralis Terquem occur in frequencies of 2 to 4% in more open, exposed platform margin sediments (Fig. 8). The two species are similar in form and distribution and represent two more (see Asterigerinidae) sharp-edged, trochoid, planispiral, calcareous perforate species occurring at the margin. Although relatively sparse, they are excellent indicators of the platform margin environment.

(9) Globigerinidae - a pelagic calcareous perforate family (Fig. 7): most individuals from this family in the Florida carbonate province belong to Globigerinoides rubra (d'Orbigny). This globose foraminifer is almost never found in sediments from depths shallower than about 9 m unless as a result of winnowing by onshore currents. Its natural nearshore occurrence is limited to the slope and outer platform margin (Fig. 8), as shown by O¹⁸ isotopic values of its tests (Emiliani, 1954; Lidz et al., 1968; Berger, 1969), as well as by its distribution in plankton tows (Jones, 1967).

(10) Miliolidae - a family most common (as much as 80% of the foraminiferal population) in the restricted interior (Figs. 2, 4, 7): Miliolinella circularis (Bornemann) is most abundant in Florida Bay (Figs. 3, 5, 6). Commonly constituting less than 1% of Florida Bay's "lake" fauna, this calcareous imperforate species shows a marked preference for mudbanks, where it averages about 10% and reaches 40% on the south side of Cross Bank (Fig. 9). It apparently can tolerate both brackish and hypersaline conditions but is absent in those areas of the open shelf exposed to oceanic water. Miliolinella circularis is one of several rotund miliolids that are concentrated in extremely shallow areas of poor circulation.

Pyrgo nasutus Cushman, a calcareous porcellanous, smooth, flanged, bichambered miliolid, occurs sparsely and sporadically in open interior and platform margin sediments. It is found at depths ranging from 0.3 to 55 m and never exceeds 2% of the population, although it is somewhat more prevalent in margin sediments (Fig. 8).

Quinqueloculina agglutinans d'Orbigny, a partially agglutinated, calcareous imperforate miliolid, is found throughout the Florida carbonate realm except for areas of brackish water (Fig. 2). It ordinarily composes 6 to 10% of foraminiferal populations both in Florida Bay and elsewhere in the platform interior (Fig. 3). In upper Florida Bay, where more extreme salinity conditions periodically exist, Q. agglutinans becomes more sparse (1%). It shows a poorly defined preference for the grainy sediments in the deeper waters of Florida Bay "lakes," where it composes as much as 20% or more of the fauna (Figs. 5, 6). The same general trend appears to hold for the platform margin, where it is most abundant in depressions between sand bars or patch reefs with better water circulation (Fig. 8).

Quinqueloculina lamarckiana d'Orbigny is found throughout the Florida platform except for the brackish environment (Fig. 2). Although its abundance varies considerably, this smooth, glossy, calcareous imperforate, fusiform miliolid normally composes about 2 to 5% of the Florida Bay mudbank fauna and commonly constitutes approximately 15% and locally 30% of the "lake" fauna (Figs. 3, 5, 6, 9). Fusiform miliolids prefer deeper water with better circulation. This differentiation is not apparent, however, in the more marine platform sediments, where it ordinarily composes 3 to 6% of the population (Fig. 8).

Quinqueloculina tenagos Parker is one of two striate, calcareous imperforate miliolid species in the area (Fig. 3). It usually occurs in abundances of 15 to 30% with local highs approaching 50% in Florida Bay (Figs. 5, 6, 9); the species is found in the shallow open interior, but its frequency in the latter sediments is very low (<3%). In both the bay and open interior, its numbers are highest near small islands, indicating a general preference for finer grained sediments.

Quinquelocutina tricarinata d'Orbigny, a distinctively fluted, calcareous imperforate miliolid, is found sparsely (2-4%) and exclusively in sediments from the platform margin; one sample (#6030) yielded a frequency of 12% (Fig. 8). The species does not occur in Florida Bay nor the open interior. Except for the fact that the species is not abundant, it is an ideal environmental indicator, is distinctive in appearance, and is closely limited in areal distribution to a narrow belt immediately behind the outer reef

Triloculina linneiana d'Orbigny, a striate, calcareous porcellanous miliolid, occurs both in Florida Bay and the platform margin. Although its occurrence and abundance are irregular, it ordinarily constitutes 3 to 6% of the foraminiferal population (Figs. 5, 6, 8). It is not found in brackish areas.

Triloculina quadrilateralis d'Orbigny, a cosmopolitan milioiid with rectangular, calcareous porcellanous chambers, is found everywhere except in very brackish areas (Fig. 2). It is most common in the center of Florida Bay, often composing 10 and sometimes more than 20% of the fauna (Figs. 5, 6, 9). Although less abundant (1-3%) in more open parts of the platform, the species is more regular and constant in distribution and frequency (Fig. 8). Depth and sediment grain size apparently are not significant factors in distribution of the species.

Triloculina rotunda d'Orbigny, an inflated, highly variable calcareous porcellanous miliolid, occurs in both Florida Bay and the open interior (Fig. 3). This species consistently constitutes 1 to 6% of the foraminifera in the open interior (Fig. 8), but it is much more abundant and persistent in Florida Bay. Triloculina rotunda seems to prefer mudbanks, as does Miliolinella circularis (see earlier discussion), and, although its frequency varies considerably, it averages about 8% of the bay fauna (Figs. 5, 6). Abundance exceeds this amount only on mudbanks and approaches 30% on Cross Bank (Fig. 9). In Florida Bay "lakes" its numbers are more consistent, regularly composing 1 to 2% of the population. The species is one of the most tolerant of the foraminifera in the bay, as it is found in brackish as well as hypersaline waters. It is, however, a shallow-water species; in outer parts of the platform it is rarely found below 9 m.

Triloculina trigonula d'Orbigny is a smooth calcareous porcellanous miliolid with variable chamber form, the test usually being somewhat longer than broad. It demonstrates a widespread, although sporadic, occurrence in shallow waters of Florida Bay and the open interior. Reaching as much as 15% (samples #A147, A148) but averaging 1 to 3% of the faunas (Figs. 5, 6, 9), it is absent in deeper waters and the more restricted areas of the bay.

(11) Rotaliidae - common in platform and margin sediments (Figs. 4, 7): Ammonia beccarii ornata (Cushman) exists in abundance under most stress conditions, including hypersaline and brackish waters. The mere proximity of land, however, is not a controlling factor. It varies in morphology: heavy-walled, multichambered, calcareous perforate tests are found in more exposed areas, very fragile tests in calmer areas, and frosted or ornamented tests in restricted and brackish areas (Fig. 3). It is most abundant in Florida Bay; the species may constitute 40 to 50% of foraminiferal populations in muddy, brackish-water sediments (Figs. 5, 6). Such sediments are typically extremely rich in tests of relatively few species. Frequency decreases as salinity increases; in areas 2 to 3 km from the mainland, the species usually composes only 3 to 6% of the fauna (Fig. 9). In "lake" deposits in Florida Bay, where coarser sediment above the Pleistocene rock floor forms only a thin veneer, the low-spired trochoidal tests are usually rough and blackened, appearing to have "weathered" in situ as there is no evidence (Scholl et al., 1969; Robbin, 1984) of subaerial exposure of Florida Bay sediments during the last 4,500 years.

(12) Soritidae - the dominant platform family, most abundant in the open interior (Figs. 2, 4, 7): Archaias angulatus (Fichtel and Moll) is the most common species in the Florida carbonate province. Compressed, with flaring, calcareous imperforate later chambers bearing cribrate apertures (Fig. 2), this extremely variable foraminifer is absent only in areas that receive influxes of fresh water, which it apparently cannot tolerate. Although its abundance varies greatly, A. angulatus averages about 20% of the foraminifera in central Florida Bay, 40% from the open platform, and 50% of those from the windward areas of the platform, which suggests that the species is more tolerant of coarse than fine sediment (Figs. 5, 6, 8, 9). Largest concentrations (as much as 80%; Rose and Lidz, 1977) are found at 6- to 9-m depths in the calm, protected lees of the shelf. On the other hand, specimens constituting 75% of the foraminiferal population are found living at Andros Island on mud flats so shallow they are periodically exposed by tides (cf. Streeter, 1963; pers. observ.) Moreover, they are exposed to extreme brackish-to-hypersaline fluctuations (Hardie, 1977; Shinn, 1983). They have also been seen in pools on North Bimini and Joulters Cays (Paul Enos, pers. comm., 1987). Apparently, variation in depth of less than 15 m has no effect on distribution of the species, but in deeper water its abundance decreases noticeably. Archaias species live freely on Thalassia and other grass blades, as well as on the sediment. The heavy, sturdy test falls to the bottom upon death of the organism and becomes part of the sediment.

Cyclorbiculina compressa (d'Orbigny), a flat, circular, highly variable calcareous imperforate soritid, occurs very sporadically in Florida Bay and open interior faunas (Fig. 6). It probably is a variant of Archaias angulatus (C. W. Poag, pers. comm., 1976). Reasons for its erratic distribution and abundance are not known. The species is not found in either brackish or hypersaline areas of the bay; however, at one site (#7386), it constituted 14% of the sampled fauna (Fig. 5), whereas it formed 25% of the fauna near the outer reef (Fig. 8).

Peneroplis proteus (d'Orbigny), an irregular, flat, calcareous imperforate species, is found on sandy, grass-covered sediments from both the protected and outer shelf areas. It is nonexistent in northeast Florida Bay but does occur in the more open western part of the bay (Figs. 5, 6). Tolerant of low salinity, the species produces aberrant tests under hypersaline conditions and is thus a valuable marker for such a degree of restriction (Hughes Clark and Keij, 1973). Preferring somewhat quieter, shallow areas open to oceanic waters, the species commonly forms 3 to 12% of the fauna from western Florida Bay and 10 to 20% of the open interior fauna (Fig. 8).

Sorites marginalis (Forskal), a very thin, waferlike, calcareous imperforate soritid, apparently prefers quiet grass-covered areas of the open interior shelf, where it reaches its greatest abundance. Normally occurring in quantities of 1 to 3%, it reaches 8 to 10% in tidal passes between Florida Bay and the open interior (Figs. 5, 6, 8). It cannot tolerate abnormal salinity, but neither does it flourish in truly oceanic water. Sorites species are non-encrusting, yet, unlike Archaias angulatus, the tests remain loosely attached via protoplasm to grass blades after death of the organism. The fragile tests are transported by currents and drop to the bottom when the plant substrate on which they raft perishes (Hughes Clark and Keij, 1973; pers. observ.).

(13) Textulariidae - limited to slope and outer margin, although other arenaceous species occur in the platform interior (Figs. 4, 7): Textularia candeiana d'Orbigny, a distinct, evenly tapering, biserial, arenaceous foraminifer, is limited, usually in abundance of <6%, to areas deeper than 6 m at the outer edges of the platform (Fig. 8). It is not found in Florida Bay nor in inner platform areas. Despite its low frequency, it is an excellent ecologic marker, distinctive both in unconsolidated sediment and in thin section.

(14) Trochamminidae-restricted to very shallow areas, preferably near shorelines: Trochammina inflata (Montagu), a coiled arenaceous foraminifer (Fig. 3), was found in 1-2% frequency in only four samples (Figs. 5, 6). Nevertheless, the species merits comment because it occurs exclusively in very shallow water in the immediate vicinity of small islands. Not seen in brackish environments or in areas of normal marine salinity, it apparently is restricted to more saline waters.

The remaining six families represented in the Florida carbonate realm, but not identified in our samples, include the infaunal calcareous perforate Buliminidae (Bulimina spp.), and the epifaunal calcareous perforate Camerinidae (Heterostegina spp.), perforate pelagic Globorotalidae (Globorotalia menardii), calcareous perforate Homotrematidae (Homotrema rubrum), calcareous perforate Nodosariidae (Lenticulina spp.), and calcareous imperforate Nubeculariidae (Spiroloculina spp.).