The study tests 3 hypotheses: a) that late Miocene to early Pliocene constriction and complete closure of the Central American Seaway (CAS), caused decreased productivity in the Caribbean, b) reduced paleoproductivity resulted in decreased diversity in the Caribbean and, c) this decreased availability of food (reduced paleoproductivity) was responsible for larger mean test size in the three most common benthic foraminiferal species Epistominella exigua, Oridorsalis umbonatus and Globocassidulina subglobosa. The hypotheses are tested by applying correlation analysis to 7 groups of paleoceanographic proxies, 3 indices of diversity measures and mean test size data from the Caribbean ODP Site 999, to 47 core samples between 8.3-2.5 Ma.Study concludes: a) the gradual closure of the CAS led Caribbean diversity and paleoproductivity to decrease abruptly at 7.9 Ma, when the nutrient-rich Pacific deep waters were cut off, and then, again with the complete closure of the seaway at 4.2 Ma, b) Caribben diversity and paleoproductivity are positively correlated and, c) that the availability of food influences mean test size; lower availability and decreased abundances lead to larger test size.