238 Recent Advances and New Voices in Marine and Coastal Geoscience

We seek abstracts on physical oceanography, marine geology, geomorphology, sediment transport, geophysics, tectonic processes, climate change, paleobiology, or any aspect of oceans and coasts, past and present. We encourage students to participate in this session.

Wednesday, 22 October 2025
8:00 AM - 12:00 PM
HBGCC, 213AB

Ecological Indicators in Tropical Reefs: Foraminiferal Assemblages Reflect Environmental Gradients in Jobos Bay, Puerto Rico

Paper number: 238-14
Program: Technical Sessions
Time: 11:30 AM – 11:45 AM

Authors

Abstract

The Jobos Bay National Estuarine Research Reserve (JBNERR), located in southeastern Puerto Rico, experiences strong environmental gradients between a historically impacted coastal plain and oligotrophic Caribbean waters. Effective monitoring of these habitats is critical, especially under the pressure of global (e.g., climate change) and local (e.g., terrestrial runoff) stressors. Resource managers require cost-effective and reliable bioindicators to monitor ecological health over time. Benthic foraminiferal assemblages offer a promising tool for assessing environmental conditions in coral reefs and seagrass ecosystems. This study evaluates the applicability of foraminiferal-based ecological indices to assess reef health across three cays in Jobos Bay: Cayo Morillo, Cayo Pájaros, and Cayo Caribe. We applied three indices: the FoRAM Index (FI), the Epiphytic FoRAM Index (FI’), and the Long-lived vs. Short-lived Span (ILS). Surficial sediment samples were collected from back-reef and fore-reef zones in 2018 and 2019. Environmental data included sediment composition (e.g., texture, total organic content) and water quality (e.g., pH). We hypothesized that foraminiferal morphogroup ratios would reflect ecological conditions. From a total of 57 samples, 4,671 individuals were counted, representing 36 genera. Cluster analysis based on genus-level relative abundance revealed four main groups: Dominant (>11%), Common (5–11%), Occasional (1–4%), and Rare (<1%). Dominant genera included Quinqueloculina (24%), Amphistegina (18%), and Discorbis (11%). Common taxa included smaller rotaliids such as Rotorbinella (6%), miliolids such as Pyrgo (5%), and symbiont-bearing epiphytic forms such as Archaias (6%). Twelve genera were occasional, including Triloculina (4%), Elphidium (3%, epiphytic form), and Laevipeneroplis (2%, symbiont-bearing). Tests of 16 genera occurred rarely (<1%), including agglutinated taxa such as Textularia, stress-tolerant forms like Bolivina, and smaller genera such as Cornuspira. In total, FI values ranged from 1.3 to 9.6, FI’ from 1.9 to 9.7, and ILS from 0.5 to 30.6. Back-reef values were generally lower (FI: 1.3–9.58; FI’: 1.9–9.6; ILS: 0.51–30.6) compared to fore-reef samples (FI: 4.9–9.4; FI’: 5.1–9.7; ILS: 2.8–27.6), indicating spatial variability in habitat quality. In sum, foraminiferal assemblages and their relative abundances reflect habitat-specific conditions, supporting their use as reliable indicators in tropical reef and seagrass environments in Puerto Rico.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414058

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