CSR strategies seasonal cycling: A new mechanism for coexistence among seaweeds.

The stable maintenance of high biological diversity remains a major puzzle in biology. We propose a new mechanism involving the cyclical use of Competitive, Stress-tolerant, and Ruderal (CSR) strategies to explain high biodiversity maintenance. This study examines the interactions among three morphs of the cosmopolitan and commercially important seaweed Ulva Linnaeus. We measured biomass productivity, effective quantum yield, carbohydrate concentration, and nutrient competition across all seasons for one year and matched trait value combinations to CSR strategies. Our findings reveal that the Ulva morphs exhibited significant competitive interactions under eutrophic conditions, in a scramble competition dynamic. However, competition did not significantly affect their functional traits under naturally prevalent oligotrophic conditions. Season-by-season analysis revealed that each morph employed temporal niche partitioning by cyclically adopting different CSR strategies, thereby avoiding direct competition. This cyclical strategy, akin to a rock-paper-scissors game, prevents any single strategy from dominating year-round, maintaining the three-morph polymorphism. Our study further highlights the importance of year-long functional trait measurements to encompass seasonal changes in functional responses. Our CSR cycling conceptual model offers new insights useful for monitoring and conservation efforts.

Linking centennial scale anthropogenic changes and sedimentary records as lessons for urban coastal management.

Coastal eutrophication and urban flooding are increasingly important components of global change. Although increased seawater renewal by barrier openings and channelizing are common mitigation measures in coastal lagoons worldwide, their effects on these ecosystems are not fully understood. Here, we evaluated the relationships between human interventions in the watershed, artificial connections to the sea, and the sediment burial rates in an urban coastal lagoon (Maricá lagoon, Southeastern Brazil). Sediment accretion along with nutrient and carbon burial rates were determined in two sediment cores representing the past ∼120 years (210Pb dating) and associated with anthropogenic changes as indicated by historical records and geoinformation analyses. Lagoon infilling and eutrophication, expressed by the average sediment accretion, TP, TN, and OC burial rates, respectively, increased ∼9-18, 13-15, 11-14 and 11-12-fold from the earliest (<1950) to the most recent (2000-2017) period. These multi-proxy records confirm mechanistic links between deforestation, urbanization, and untreated sewage discharges. In addition, our findings reveal artificial connections to the sea may contribute to lagoonal eutrophication and infilling, particularly when not integrated with sewage treatment and forest conservation or reforestation in the watershed. Therefore, increased seawater renewal by physical interventions commonly considered as mitigation measures may in contrast cause severe degradation in coastal lagoons, causing harmful consequences that should be not neglected when implementing management practices.

Immediate and residual effects of low-dose nandrolone decanoate and treadmill training on adipose and reproductive tissues of male Wistar rats.

CONTEXT: Residual effects after nandrolone decanoate (ND) treatment are not reported. OBJECTIVE: Immediate and residual effects of low-dose ND and treadmill training were investigated. MATERIALS AND METHODS: Male rats were trained and/or ND-treated for four weeks and the assessments were made after this period or four weeks later. RESULTS: The groups did not differ in final plasma glucose or AUC of the ivGTT, but hyperinsulinemia was noticed in some trained/treated groups. Training with ND increased muscle mass and ND decreased the reproductive structures. Decreased fat with training was reversed by detraining. DISCUSSION: The anabolic action of ND on skeletal muscle was enhanced by training. Fat and lipid changes were more linked to training/detraining, but the effects of ND on the reproductive structures persisted after treatment. CONCLUSIONS: The effects of training on fat and muscle were not maintained after detraining, but low-dose ND had persistent effects on the reproductive structures.