Holocene trends in distribution and diversity of benthic foraminifera assemblages in atoll lagoons, Belize, Central America

Abstract

Seven benthic foraminiferal assemblages were identiWed in vibracores through Holocene lagoons of three Belize atoll lagoons (Glovers Reef, Lighthouse Reef, TurneVe Islands). These include (1) the low-diversity Cribroelphidium assemblage (2) the CribroelphidiumElphidium assemblage (3) the Quinqueloculina-Triloculina-Peneroplis assemblage (4) the high-diversity miliolid assemblage (5) the Archaias-miliolid assemblage (6) the low-diversity miliolid assemblage, and (7) the mixed assemblage. Altogether, 109 species and 56 genera were identiWed. The highest diversities are observed in the largest lagoon (TurneVe Islands), whereas one of the smaller lagoons (Glovers Reef) exhibits the lowest diversities during the Holocene. No signiWcant changes in diversity over time occur, however, a slight trend to higher diversity may be observed through the Holocene, suggesting that the foraminiferal faunas in the atolls are in a diversiWcation stage. Faunal diversity in atoll lagoons appears to be controlled largely by habitat size, habitat heterogeneity, and water circulation. Habitat age and water depth only play minor roles. Substrate texture, water depth, and turbidity inXuence the predominant modes of life of benthic foraminifera encountered in the lagoons (epifaunal versus infaunal versus symbiont-bearing). Time-averaging eVects were not observed, even though lagoonal sedimentation rates Xuctuate in individual cores and the three lagoons, and despite the fact that sediments are modiWed through bioturbation by callianassid shrimps. This Wnding underlines the potential of benthic foraminifera for paleoecological studies in the fossil record of reefs and carbonate platforms.

Anatomy of the Holocene inundation of an isolated carbonate platform: Bermuda North Lagoon, western Atlantic

“…Similar observations were made in other Holocene lagoons of atolls (Gischler, 2003; and isolated barrier reef systems (Isaack et al, 2016;Zinke, Reijmer, Thomassin, Dullo, et al, 2003;Zinke et al, 2005). Especially in the early Holocene deposits, there are usually lag times of up to 2 kyr between the first marine carbonate sediments and underlying mangrove peat deposits suggesting that a certain amount of time is necessary until the marine carbonate factory has been fully established (Isaack et al, 2016;Kim, Fouke, Quinn, Kerans, & Taylor, 2012;Schultz et al, 2010;Tipper, 1997). A principal problem in this context is the fact that complete transgressive lagoonal successions are best developed only in the deepest lagoon parts, where Holocene sediment thickness usually reaches or even exceeds 10 m (Isaack et al, 2016;Zinke et al, 2001).…”

“…These findings have important implications for analysing carbonate platforms in the fossil record, especially for sequence stratigraphy and cyclostratigraphy where sea-level sequences are supposed to be characterized by filled accommodation space, i.e., where cycle thickness is supposed to approximately equal sea-level variation. In addition to sedimentological projects, detailed foraminiferal studies with atoll lagoon cores were made in the Marshall Islands (Yamano, Kayanne, Matsuda, & Tsuji, 2002), offshore Belize (Schultz, Gischler, & Oschmann, 2010), and in the Maldives (Storz, Gischler, Parker, & Klostermann, 2014). Coarse-grained layers within fine background sediments of atoll and oceanic barrier reef lagoons were used to identify echinoid die-off events in Belize (Gischler, 2010), tsunami sedimentation in the Maldives (Klostermann, Gischler, Storz, & Hudson, 2014) and tempestite deposition in French Polynesia (Toomey, Donnelly, & Woodruff, 2013).…”

Holocene tropical reef accretion and lagoon sedimentation: A quantitative approach to the influence of sea‐level rise, climate and subsidence (Belize, Maldives, French Polynesia)

“…Vibracore thickness and sample elevation were corrected for compaction (Table S1); recovery in all vibracores is 100%. Vibracores include 11 cores from Belize atoll lagoons (Gischler, 2003;Schultz, Gischler, & Oschmann, 2010), 11 cores from the lagoon at Rasdhoo Atoll (Klostermann & Gischler, 2015) and 6 cores from the Bora Bora lagoon . Individual lagoon cores are up to 6 m long (average 3.8 m; total 111.5 m) and largely comprise packstone, wackestone and mudstone with abundant mollusc, foraminifer and Halimeda remains ( Figure 4).…”