Shifts in biodiversity and physical structure of seagrass beds across 5 decades at Carriacou, Grenadines

for richness; F2,48 = 7.3, P <0.002 for diversity) (Fig 6). In 1994, richness and diversity were significantly greater (by 2- and 1.4-fold respectively; Tukey HSD test, P <0.01) than in 1969 or 2016, when both measures did not differ (P > 0.96). The overall composition of the benthic community also differed significantly across years (PERMANOVA, P = 0.001) with a similar pattern of between-year differences: community composition was less similar between 1994 Fig 5. Frequency of occurrence of more common species of macroalgae and sessile macroinvertebrates, and of sea urchins, at stations (n = 17) in 1969, 1994, 2016. Mean (+ SE) frequency (%) in 12 quadrats per station. Green algae: Avrainvillea nigricans (AvNi*), Avrainvillea rawsonii (AvRa*), Dictyosphaeria cavernosa (DiCa*), Halimeda incrassata (HaInc), Halimeda opuntia (HaOpu), Udotea cyathiformis (UdCya), Udotea flabellum (UdFla), Valonia ventricosa (VaVe*); brown algae: Canistrocarpus cervicornis (CaCer), Dictyopteris delicatula (DiDel), Dictyopteris justii (DiJu*), Dictyota ciliolata (DiCil), Dictyota dichotoma (DiDic), Dictyota implexa (DiImp), Dictyota mertensii (DiMer); Caulerpa: Caulerpa cupressoides (CaCup), Caulerpa cupressoides var. lycopodium (CaLyc), Caulerpa mexicana (CaMex), Caulerpa prolifera (CaPro), Caulerpa scalpelliformis (CaSca), Caulerpa sertularioides (CaSer); red algae: Amphiroa fragilissima (AmFra), Amphiroa rigida (AmRig), Amphiroa tribulus (AmTri), Hypnea cervicornis (HyCer), coral: Manicina areolata (MaAre), Porites Furcata

(PoFu*); sponges: Amphimedon erina (AmEri), Cliona varians (ClVar), Halichondria melanodocia (HaMe*), Hyrtios violaceus (HyVio), Tedania ignis (TeIgn); sea urchins: Tripneustes ventricosus (TrVe*). https://doi.org/10.1371/journal.pone.0306897.g005 PLOS ONE Seagrass bed biodiversity and structure and across 5 decades PLOS ONE | https://doi.org/10.1371/journal.pone.0306897 August 1, 2024 11 / 25