Herbivore effects increase with latitude across the extent of a foundational seagrass.

Climate change is altering the functioning of foundational ecosystems. While the direct effects of warming are expected to influence individual species, the indirect effects of warming on species interactions remain poorly understood. In marine systems, as tropical herbivores undergo poleward range expansion, they may change food web structure and alter the functioning of key habitats. While this process ('tropicalization') has been documented within declining kelp forests, we have a limited understanding of how this process might unfold across other systems. Here we use a network of sites spanning 23° of latitude to explore the effects of increased herbivory (simulated via leaf clipping) on the structure of a foundational marine plant (turtlegrass). By working across its geographic range, we also show how gradients in light, temperature and nutrients modified plant responses. We found that turtlegrass near its northern boundary was increasingly affected (reduced productivity) by herbivory and that this response was driven by latitudinal gradients in light (low insolation at high latitudes). By contrast, low-latitude meadows tolerated herbivory due to high insolation which enhanced plant carbohydrates. We show that as herbivores undergo range expansion, turtlegrass meadows at their northern limit display reduced resilience and may be under threat of ecological collapse.

Novel pathogenic variant of DICER1 in an adolescent with multinodular goiter, ovarian Sertoli-Leydig cell tumor and pineal parenchymal tumor of intermediate differentiation.

OBJECTIVES: To present a case of a new pathogenic variant of DICER1. CASE PRESENTATION: 13-year-old female with non-toxic multinodular goiter and ovarian Sertoli-Leydig cell tumor, in whom a pineal parenchymal tumor of intermediate differentiation was diagnosed. Next-generation sequencing revealed a new germline mutation in the DICER1 gene (exon 16, c2488del [pGlu830Serfs*2] in heterozygosis), establishing the diagnosis of DICER1 syndrome. CONCLUSIONS: Mutations in the DICER1 gene cause genetic predisposition to a wide spectrum of benign or malignant tumors from childhood to adulthood.

Nutrient availability induces community shifts in seagrass meadows grazed by turtles.

In the Caribbean, green turtles graze seagrass meadows dominated by Thalassia testudinum through rotational grazing, resulting in the creation of grazed and recovering (abandoned) patches surrounded by ungrazed seagrasses. We evaluated the seagrass community and its environment along a turtle grazing gradient; with the duration of (simulated) grazing as a proxy for the level of grazing pressure. The grazing levels consisted of Short-term (4 months clipping), Medium-term (8 months clipping), Long-term grazing (8 months of clipping in previously grazed areas), 8-months recovery of previously grazed patches, and ungrazed or unclipped patches as controls. We measured biomass and density of the seagrasses and rhizophytic algae, and changes in sediment parameters. Medium- and Long-term grazing promoted a shift in community species composition. At increasing grazing pressure, the total biomass of T. testudinum declined, whereas that of early-successional increased. Ammonium concentrations were highest in the patches of Medium-term (9.2 + 0.8 µM) and Long-term grazing levels (11.0 + 2.2 µM) and were lowest in the control areas (4.6 + 1.5 µM). T. testudinum is a late-successional species that maintains sediment nutrient concentrations at levels below the requirements of early-successional species when dominant. When the abundance of this species declines due to grazing, these resources become available, likely driving a shift in community composition toward a higher abundance of early-successional species.