Ligia Collado-Vides

Spatio-temporal patterns and nutrient status of macroalgae in a heavily managed region of Biscayne Bay, Florida, USA

Abstract The coastal bays of South Florida are located downstream of the Florida Everglades, where a comprehensive restoration plan will strongly impact the hydrology of the region. Submerged aquatic vegetation communities are common components of benthic habitats of Biscayne Bay, and will be directly affected by changes in water quality. This study explores community structure, spatio-temporal dynamics, and tissue nutrient content of macroalgae to detect and describe relationships with water quality. The macroalgal community responded to strong variability in salinity; three distinctive macroalgal assemblages were correlated with salinity as follows: (1) low-salinity, dominated by Chara hornemannii and a mix of filamentous algae; (2) brackish, dominated by Penicillus capitatus, Batophora oerstedii, and Acetabularia schenckii; and (3) marine, dominated by Halimeda incrassata and Anadyomene stellata. Tissue-nutrient content was variable in space and time but tissues at all sites had high nitrogen and N:P values, demonstrating high nitrogen availability and phosphorus limitation in this region. This study clearly shows that distinct macroalgal assemblages are related to specific water quality conditions, and that macroalgal assemblages can be used as community-level indicators within an adaptive management framework to evaluate performance and restoration impacts in Biscayne Bay and other regions where both freshwater and nutrient inputs are modified by water management decisions.

Halophila stipulacea (Hydrocharitaceae): A Recent Introduction to the Continental Waters of Venezuela

Abstract The occurrence of the introduced seagrass Halophila stipulacea (Hydrocharitaceae) is reported for Puerto Azul, Playa Mansa, Venezuela. This record documents range expansion to the Caribbean mainland, and first observation of male flowers, of this introduced seagrass, which until April 2013 was only reported at several Caribbean islands.

Practical applications of monitoring results to improve managing for coral reef resilience: a case study in the Mexican Caribbean

Marine protected areas (MPAs) are promoted as an effective strategy to balance human use and conservation of marine resources, yet case studies have shown mixed results regarding MPA success. Managing to promote resilience is widely recognized as a priority for MPAs that focus on the conservation of coral reefs and the ecological services they provide. To this end, there is an acute need to develop and implement methods that assimilate monitoring results into comprehensive summaries that can be understood and acted upon by local management to promote resilience. We used the Parque Nacional Arrecife de Puerto Morelos (PNAPM) as a model MPA to evaluate the utility of a resilience index framework proposed by Maynard et al. (Coral Reefs 29:381–391, 2010b) that uses a suite of broad- and local-scale indicators to rank the relative resilience of sites. Based on monitoring data we identify local stressors adversely impacting coral reef resilience that can be influenced by management actions. Improving regulation enforcement, conducting targeted invasive species removals, reallocating and restricting tourist activities, and establishing nutrient level regulations were identified as realistic adaptive management actions to promote resilience within the PNAPM. This first application of the Maynard et al. (Coral Reefs 29:381–391, 2010b) resilience index framework to a Caribbean MPA provides an example for MPA managers of the value of their monitoring data and the utility of a broadly applicable management tool to assist in managerial decisions. Moving beyond simply monitoring sites to management action is essential to promote resilience and maintain the health and existence of coral reef ecosystems.

Seasonal regulation of herbivory and nutrient effects on macroalgal recruitment and succession in a Florida coral reef

Herbivory and nutrient enrichment are drivers of benthic dynamics of coral reef macroalgae; however, their impact may vary seasonally. In this study we evaluated the effects of herbivore pressure, nutrient availability and potential propagule supply on seasonal recruitment and succession of macroalgal communities on a Florida coral reef. Recruitment tiles, replaced every three months, and succession tiles, kept in the field for nine months, were established in an ongoing factorial nutrient enrichment-herbivore exclusion experiment. The ongoing experiment had already created very different algal communities across the different herbivory and nutrient treatments. We tracked algal recruitment, species richness, and species abundance through time. Our results show seasonal variation in the effect of herbivory and nutrient availability on recruitment of coral reef macroalgae. In the spring, when there was higher macroalgal species richness and abundance of recruits, herbivory appeared to have more control on macroalgal community structure than did nutrients. In contrast, there was no effect of either herbivory or nutrient enrichment on macroalgal communities on recruitment tiles in cooler seasons. The abundance of recruits on tiles was positively correlated with the abundance of algal in the ongoing, established experiment, suggesting that propagule abundance is likely a strong influence on algal recruitment and early succession. Results of the present study suggest that abundant herbivorous fishes control recruitment and succession of macroalgae, particularly in the warm season when macroalgal growth is higher. However, herbivory appears less impactful on algal recruitment and community dynamics in cooler seasons. Ultimately, our data suggest that the timing of coral mortality (e.g., summer vs. winter mortality) and freeing of benthic space may strongly influence the dynamics of algae that colonize open space.

Severe impacts of brown tides caused by Sargassum spp. on near-shore Caribbean seagrass communities

From mid-2014 until the end of 2015, the Mexican Caribbean coast experienced a massive influx of drifting Sargassum spp. that accumulated on the shores, resulting in build-up of decaying beach-cast material and near-shore murky brown waters (Sargassum-brown-tides, Sbt). The effects of Sbt on four near-shore waters included reduction in light, oxygen (hypoxia or anoxia) and pH. The monthly influx of nitrogen, and phosphorus by drifting Sargassum spp. was estimated at 6150 and 61kgkm-1 respectively, resulting in eutrophication. Near-shore seagrass meadows dominated by Thalassia testudinum were replaced by a community dominated by calcareous rhizophytic algae and drifting algae and/or epiphytes, resulting in 61.6-99.5% loss of below-ground biomass. Near-shore corals suffered total or partial mortality. Recovery of affected seagrass meadows may take years or even decades, or changes could be permanent if massive influxes of Sargassum spp. recur.

Morphological and physiological responses of seagrasses (Alismatales) to grazers (Testudines: Cheloniidae) and the role of these responses as grazing patch abandonment cues

Green sea turtles, Chelonia mydas, are grazers influencing the distribution of seagrass within shallow coastal ecosystems, yet the drivers behind C. mydas patch use within seagrass beds are largely unknown. Current theories center on food quality (nutrient content) as the plant responds to grazing disturbances; however, no study has monitored these parameters in a natural setting without grazer manipulation. To determine the morphological and physiological responses potentially influencing seagrass recovery from grazing disturbances, seagrasses were monitored for one year under three different grazing scenarios (turtle grazed, fish grazed and ungrazed) in a tropical ecosystem in Akumal Bay, Quintana Roo, Mexico. Significantly less soluble carbohydrates and increased nitrogen and phosphorus content in Thalassia testudinum were indicative of the stresses placed on seagrasses during herbivory. To determine if these physiological responses were the drivers of the heterogeneous grazing behavior by C. mydas recorded in Akumal Bay, patches were mapped and monitored over a six-month interval. The abandoned patches had the lowest standing crop rather than leaf nutrient or rhi- zome soluble carbohydrate content. This suggests a modified Giving Up Density (GUD) behavior: the critical threshold where cost of continued grazing does not provide minimum nutrients, therefore, new patches must be utilized, explains resource abandonment and mechanism behind C. mydas grazing. This study is the first to apply GUD theory, often applied in terrestrial literature, to explain marine herbivore grazing behavior.

New perspectives on an iconic landscape from comparative international long-term ecological research

Iconic ecosystems like the Florida Coastal Everglades can serve as sentinels of environmental change from local to global scales. This characteristic can help inform general theory about how and why ecosystems transform, particularly if distinctive ecosystem properties are studied over long time scales and compared to those of similar ecosystems elsewhere. Here we review the ways in which long-term, comparative, international research has provided perspectives on iconic features of the Everglades that have, in turn, informed general ecosystem paradigms. Studies in other comparable wetlands from the Caribbean to Australia have shed light on distinctive and puzzling aspects such as the “upside-down estuary” and “productivity paradox” for which the Everglades is known. These studies suggest that coastal wetlands on carbonate (karstic) platforms have: (1) hydrological and biogeochemical properties that reflect “hidden” groundwater sources of water and nutrients, (2) very productive, mat-forming algal communities that present a low-quality food to aquatic consumers that encourages (3) highly diversified feeding strategies within and among populations, and (4) extensive and productive seagrass meadows and mangrove forests that promote strong cultural dependencies associated with the ecosystem services they provide. The contribution of international research to each of these general ecological topics is discussed with a particular goal of encouraging informed decision-making in threatened wetlands across the globe.

Molecular and morphological characterization of Laurencia intricata and Laurenciella mayaimii sp. nov. (Ceramiales, Rhodophyta) in South Florida, USA

Abstract: Morphological characterization, together with phylogenetic and DNA barcoding analyses on the basis of rbcL and COI-5P, conducted on some species of the Laurencia complex in South Florida confirmed the occurrence of Laurencia intricata and supported the presence and recognition of Laurenciella in the United States. Samples of L. intricata from Florida grouped with full support with the species from the type locality (Antilles). The intraspecific divergence within the L. intricata clade ranged from 0.0% to 1.3%; the samples from Florida diverged by only 0.06% to 0.20%, the sample from Mexico (EF658643 – Puerto Morelos, Quintana Roo) being the most divergent. The two new species of Laurenciella from Florida, La. mayaimii and La. sp., formed an assemblage with La. marilzae with full support, and the interspecific divergence was high for both molecular markers. Laurenciella mayaimii is characterized mainly by its brownish-yellow main axis and cylindrical, alternate to subopposite branchlets, anastomoses between branches in the basal portions, and a single ‘corps en cerise’ present in each cortical cell and in trichoblasts. In addition, the walls of the cortical cells near the apices project, and lenticular thickenings are absent. The finding of Laurenciella in Biscayne Bay and Key Largo, South Florida expands its geographic distribution to western Atlantic lower subtropical waters.

Interactive effects of herbivory and substrate orientation on algal community dynamics on a coral reef

Herbivory is a significant driver of algal community dynamics on coral reefs. However, abiotic factors such as the complexity and orientation of the benthos often mediate the impact of herbivores on benthic communities. We experimentally evaluated the independent and interactive effects of substrate orientation and herbivorous fishes on algal community dynamics on a coral reef in the Florida Keys, USA. We created horizontal and vertical substrates, mimicking the trend in the reduction of vertical surfaces of coral reefs, to assess how algal communities developed either with herbivory (open areas) or without herbivory (herbivore exclosures). We found that substrate orientation was the dominant influence on macroalgal community composition. Herbivores had little impact on community development of vertical substrates as crustose algae dominated these substrates regardless of being in exclosures or open areas. In contrast, herbivores strongly impacted communities on horizontal substrates, with upright macroalgae (e.g., Dictyota spp., articulated coralline algae) dominating herbivore exclosures, while filamentous turf algae and sediment dominated open areas. Outside of exclosures, differences between vertical and horizontal substrates exposed to herbivores persisted despite similar intensity of herbivory. Our results suggest that the orientation of the reef benthos has an important impact on benthic communities. On vertical surfaces, abiotic factors may be more important for structuring algal communities while herbivory may be more important for controlling algal dynamics in flatter areas. Thus, the decline in structural complexity of Caribbean coral reefs and the flattening of reef substrates may fundamentally alter the impact that herbivores have on benthic community dynamics.