Shifting sources of productivity in the coastal marine tropics during the Cenozoic era

Abstract

Changes in the rates and sources of marine primary production over time are difficult to document owing to the absence of direct estimates of past productivity. Here, I use the maximum body sizes of the largest species in each of 23 tropical shallow-water marine molluscan guilds (groups of species with similar habits and trophic roles) to trace the relative importance of planktonic and benthic primary productivity from the Eocene (55 Ma) onwards. The largest members of guilds are least constrained in exploiting resources and therefore reflect the availability and accessibility of those resources most accurately. Maximum sizes of suspension-feeders and predators increased by a factor of 2.3 and 4.0, respectively, whereas those in four out of five herbivorous guilds declined. I interpret these patterns, which are discernible throughout the coastal tropics, to mean that primary production in the Eocene marine tropics was concentrated on the seafloor, as is the case today on offshore reefs and islands, and that the Miocene to the recent interval witnessed a dramatic increase in planktonic productivity along continental margins. The rise in planktonic fertility is best explained by an increase in nutrient supply from the land associated with intense global tectonic activity and more vigorous ocean mixing owing to cooling.

Revisión de la Subfamilia Crassatellinae (Bivalvia: Crassatellidae) del Paleógeno—Neógeno de Argentina

“…Ocean cooling may have played an indirect role (Berggren and Prothero 1992), or a shift from predominantly benthic to planktonic primary production (Vermeij 2011), or the rapid diversification at the generic level of competing infaunal siphonate bivalves (Stanley 1968). Why Neogene crassatellines were able to occupy deeper or quieter water niches that they had not previously favored is also not known.…”

The evolution of molluscan photosymbioses: a critical appraisal

“…Unlike other neritids and members of the Neritopsina generally, Velates has a large, conical, limpet‐like shell (maximum diameter 190 mm; Woodring, ) that, in life, was completely enveloped by the mantle, as indicated by a polished outer layer extending from the basal callus (Savazzi, ; Vermeij, ). Velates has been interpreted either as a suspension‐feeder (Savazzi, ) or herbivore (Vermeij, ), although its large size, exposure of the mantle to light, and distribution in well‐lit tropical carbonate‐dominated environments are also consistent with photosymbiosis.…”

“…Tridacnine and fragine bivalves, as well as reef‐building photosymbiotic corals, foraminifers, sponges, and didemnid tunicates, are most diverse and abundant and reach larger maximum body sizes in the inner Indo‐West Pacific, where conditions vary from oligotrophic to mesotrophic (Birkeland, ; Perry et al ., ) than around oligotrophic offshore atolls. All these groups diversified during the Miocene and Pliocene at times when tropical seas were on the whole less oligotrophic than they are today (Vermeij, ). The maximum size among tridacnine giant clams increased greatly from the Early to the Late Miocene (Harzhauser et al ., ) despite greater nutrient supplies in the inner Indo‐West Pacific.…”

“…Other molluscan clades with photosymbiotic members but lacking shells are also restricted to the Indo‐West Pacific, including the aeolidoidean nudibranch genera Pteraeolidia and Phyllodesmium (Burghardt et al ., ; Moore & Gosliner, ). High productivity during most of the Miocene and Pliocene in tropical America (O'Dea et al ., ; Vermeij, ) may have prevented the survival or origin of photosymbiotic molluscan lineages there. However, photosymbiotic corals, benthic foraminifers, and sacoglossan opisthobranchs were diverse in tropical America during this interval (Pochon & Pawlowski, ; Johnson, Jackson & Budd, ), and lineages of Symbiodinium in the Caribbean diverged from those in the Indo‐West Pacific during or before the Early Miocene (LaJeunesse, ).…”

Paleophysiology: From Fossils to the Future

“…These new groups have prospered as increased mountain building and the expansion of grasslands fertilized the ocean [76][77][78][79]. In attached seaweeds, rapid nutrient uptake and transport is indicated by a highly branched morphology and, in species with large blades, a complex 3D surface [80,81].…”