High-resolution Spatiotemporal Dynamics of Harmful Algae in the Indian River Lagoon (Florida)-A Case Study of Aureoumbra lagunensis, Pyrodinium bahamense, and Pseudo-nitzschia

Kratosvirus quantuckense: the history and novelty of an algal bloom disrupting virus and a model for giant virus research

Since the discovery of the first "giant virus," particular attention has been paid toward isolating and culturing these large DNA viruses through Acanthamoeba spp. bait systems. While this method has allowed for the discovery of plenty novel viruses in the Nucleocytoviricota, environmental -omics-based analyses have shown that there is a wealth of diversity among this phylum, particularly in marine datasets. The prevalence of these viruses in metatranscriptomes points toward their ecological importance in nutrient turnover in our oceans and as such, in depth study into non-amoebal Nucleocytoviricota should be considered a focal point in viral ecology. In this review, we report on Kratosvirus quantuckense (née Aureococcus anophagefferens Virus), an algae-infecting virus of the Imitervirales. Current systems for study in the Nucleocytoviricota differ significantly from this virus and its relatives, and a litany of trade-offs within physiology, coding potential, and ecology compared to these other viruses reveal the importance of K. quantuckense. Herein, we review the research that has been performed on this virus as well as its potential as a model system for algal-virus interactions.

Eutrophication leads to food web enrichment and a lack of connectivity in a highly impacted urban lagoon

Nitrogen (N) loading can affect estuarine food webs through alteration of primary producers. In the Indian River Lagoon (IRL), Florida there has been long-term N enrichment, worsening phytoplankton blooms, large-scale macroalgal blooms, and catastrophic seagrass losses. To investigate how N enrichment affects higher trophic levels and food webs in the IRL, nutrient availability was compared to primary producer and faunal stable N (δ15N) isotope values. Seawater samples were collected in the IRL for dissolved nutrient, chlorophyll-a, and particulate organic matter δ15N analyses. Macrophytes and fauna were also collected for δ15N analyses. Throughout the IRL, N was elevated but was highest in the northern IRL and Banana River Lagoon. δ15N was enriched in these segments for most samples to levels characteristic of human-waste impacted estuaries. Variability in δ15N among lagoon segments suggests a low level of trophic connectivity. Decreasing N loading to the IRL and other eutrophic estuaries may help improve resiliency.

MORBIDITY AND MORTALITY PATTERNS OF INDIAN RIVER LAGOON COMMON BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS TRUNCATUS) 2002-2020

Mortality patterns in cetaceans are critical to understanding population health. Common bottlenose dolphins (Tursiops truncatus truncatus) inhabiting the Indian River Lagoon (IRL), Florida have been subjected to four unusual mortality events (UMEs), highlighting the need to evaluate morbidity and mortality patterns. Complete gross examinations were conducted on 392 stranded dolphins and histopathological analyses were conducted for 178 animals (2002-2020). The probable causes of mortality were grouped by etiologic category: degenerative, metabolic, nutritional, inflammatory (infectious and noninfectious disease), and trauma. Probable cause of mortality was determined in 57% (223/392) of cases. Inflammatory disease (infectious/noninfectious) and trauma were the most common. Inflammatory disease accounted for 41% of cases (91/223), with the lungs (pneumonia) most commonly affected. Trauma accounted for 36% of strandings (80/223). The majority of trauma cases were due to anthropogenic activities (entanglement, fishing gear or other debris ingestion, and propeller strikes), accounting for 58% of trauma cases (46/80). Natural trauma (prey-associated esophageal obstruction or asphyxiation, shark bites, and stingray interactions) accounted for 12% of all cases (26/223), and trauma of undetermined origin was identified in 4% of cases (8/223). Starvation or inanition (nutritional) were the probable cause of mortality in 17% of cases and peaked during the 2013 UME (61% of cases). Degenerative and metabolic etiologies accounted for 5% of cases. This study represents the most comprehensive evaluation of morbidity and mortality patterns in IRL dolphins. Because IRL dolphins are routinely exposed to anthropogenic threats and have endured multiple UMEs, these baseline data are critical to the conservation and management of this population.

Pseudo-nitzschia species, toxicity, and dynamics in the southern Indian River Lagoon, FL

The Indian River Lagoon (IRL) spans approximately one-third of the east coast of Florida and, in recent years, has faced frequent harmful algal blooms (HABs). Blooms of the potentially toxic diatom, Pseudo-nitzschia, occur throughout the lagoon and were reported primarily from the northern IRL. The goal of this study was to identify species of Pseudo-nitzschia and characterize their bloom dynamics in the southern IRL system where monitoring has been less frequent. Surface water samples collected from five locations between October 2018 and May 2020 had Pseudo-nitzschia spp. present in 87% of samples at cell concentrations up to 1.9×10³ cells mL^-1. Concurrent environmental data showed Pseudo-nitzschia spp. were associated with relatively high salinity waters and cool temperatures. Six species of Pseudo-nitzschia were isolated, cultured, and characterized through 18S Sanger sequencing and scanning electron microscopy. All isolates demonstrated toxicity and domoic acid (DA) was present in 47% of surface water samples. We report the first known occurrence of P. micropora and P. fraudulenta in the IRL, and the first known DA production from P. micropora.

Variability patterns and phenology of harmful phytoplankton blooms off southern Portugal: Looking for region-specific environmental drivers and predictors

Harmful algal blooms (HABs) negatively impact coastal ecosystems, fisheries, and human health, and their prediction has become imperative for effective coastal management. This study aimed to evaluate spatial-temporal variability patterns and phenology for key toxigenic phytoplankton species off southern Portugal, during a 6-year period, and identify region-specific environmental drivers and predictors. Total abundance of species responsible for amnesic shellfish poisoning (Pseudo-nitzschia spp.), diarrhetic shellfish poisoning (Dinophysis spp.), and paralytic shellfish poisoning (G. catenatum) were retrieved, from the National Bivalve Mollusk Monitoring System public database. Contemporaneous environmental variables were acquired from satellite remote sensing, model-derived data, and in situ observations, and generalized additive models (GAMs) were used to explore the functional relationships between HABs and environmental variables and identify region-specific predictors. Pseudo-nitzschia spp. showed a bimodal annual cycle for most coastal production areas, with spring and summer maxima, reflecting the increase in light intensity during the mixed layer shoaling stage, and the later stimulatory effects of upwelling events, with a higher bloom frequency over coastal areas subjected to stronger upwelling intensity. Dinophysis spp. exhibited a unimodal annual cycle, with spring/summer maxima associated with stratified conditions, that typically promote dinoflagellates. Dinophysis spp. blooms were delayed with respect to Pseudo-nitzschia spp. spring blooms, and followed by Pseudo-nitzschia spp. summer blooms, probably reflecting upwelling-relaxation cycles. G. catenatum occurred occasionally, namely in areas more influenced by river discharges, under weaker upwelling. Statistical-empirical models (GAMs) explained 7-8%, and 21-54% of the variability in Pseudo-nitzschia spp. and Dinophysis spp., respectively. Overall, a set of four easily accessible environmental variables, surface photosynthetically available radiation, mixed layer depth, sea surface temperature, and chlorophyll-a concentration, emerged as the most influential predictors. Additionally, over the coastal production areas along the south coast, river discharges exerted minor negative effects on both HAB groups. Despite evidence supporting the role of upwelling intensity as an environmental driver of Pseudo-nitzschia spp., it was not identified as a relevant model predictor. Future model developments, such as the inclusion of additional environmental variables, and the implementation of species- and period-specific, and hybrid modelling approaches, may further support HAB operational forecasting and managing over complex coastal domains.