Gracilaria parva sp. nov. (Gracilariales, Rhodophyta) a Diminutive Species from the Tropical Eastern Pacific

DNA sequencing of the plastid encoded rbcL gene supported by morpho-anatomical features reveals Gracilaria parva sp. nov. from Panama and Ecuador in the tropical eastern Pacific Ocean. In the rbcL phylogram, G. parva occurs in a clade sister to the western Atlantic species G. galatensis. Morphologically and anatomically, G. parva is distinguished from two similar, described tropical eastern Pacific species, G. brevis and G. veleroae by its small size, to 2.5 cm tall with branch widths mostly <2 mm occasionally to 4 mm, and by its two to three cell layered cortex. Gracilaria brevis and G. veleroae are taller, have wider branches, and a one cell layered cortex. DNA sequencing is needed to resolve the many diminutive species in the tropical eastern Pacific, particularly those occurring in turf communities. DNA sequencing of historical type specimens from the 19th and 20th centuries is also needed to correctly apply names in this region.

Fishers' Ecological Knowledge and Stable Isotope Analysis Reveal Mangrove Estuaries as Key Developmental Habitats for Critically Endangered Sea Turtles

Successful conservation of endangered, migratory species requires an understanding of habitat use throughout life stages. When dedicated scientific studies are difficult to conduct, local expert knowledge can provide crucial baseline data to guide study design and aid data interpretation. In 2008, fishers in El Salvador demonstrated that eastern Pacific hawksbill sea turtles (Eretmochelys imbricata)—a population conservation biologists considered virtually extirpated—use mangrove estuaries as nesting habitat rather than open-coast beaches used by hawksbills in other regions. We confirmed and amplified this observation by using fishers' ecological knowledge to guide biological sampling for stable isotope analysis to assess if eastern Pacific hawskbills use mangrove-dominated estuaries as developmental habitats. We found that immature hawksbills experience a pelagic stage and then recruit to estuaries at ~37 cm curved carapace length, where they increase reliance on estuarine resources until they approach adult sizes. This life history strategy makes them especially vulnerable to in-water nearshore threats, and necessitates targeted expansion of conservation efforts throughout the eastern Pacific. Our analysis also provides a model for integrating traditional scientific approaches with local knowledge—a model that could yield crucial advances in other understudied regions.

The Effects of Climatic Variability on the Feeding Ecology of the Scalloped Hammerhead Shark (Sphyrna lewini) in the Tropical Eastern Pacific

Climatic variability changes ocean productivity and generates systematic cascading effects in marine food webs. Studying the feeding ecology of top predators, such as sharks, can provide insights into the overall health of marine ecosystems. We conducted a 4-year study to evaluate seasonal and inter-annual trophic variations and their relationship with El Niño Southern Oscillation (ENSO) on the largest aggregation of scalloped hammerhead shark (Sphyrna lewini) in the Tropical Eastern Pacific (TEP). We used δ13C and δ15N signatures to gain a better understanding of hammerheads’ feeding strategies as well as variations of their isotopic niche. Our results suggest that the hammerhead sharks in the Galapagos Marine Reserve respond to climatic fluctuations, with La Niña event potentially benefiting their trophic needs as the overall marine productivity increased in the region. This work is the first of its kind in the TEP and provides insights on how climate variability influences the feeding ecology of this critically endangered species. It also highlights the need to incorporate climate-related conservation strategies into the management of this species since ENSO events become more frequent and intense in the face of climate change.

Presence of Conchoderma auritum and C. virgatum (Maxillopoda, Lepadidae) and Gloiopotes huttoni (Copepoda, Caligidae) on the black marlin, from the Gulf of Tehuantepec, Mexico

This is the first report of coexistence of pedunculate barnacles, Conchoderma auritum and C. virgatum in the mouth, and with the copepod Gloiopotes huttoni in the precaudal zone, on the black marlin, Istiompax indica, a as host. This is also the first note of a new non-mammalian host for C. auritum. The host specimen was caught in sport fishing in the Gulf of Tehuantepec, eastern Pacific. A review of registered occurrences of the genus Conchoderma in species of the fish family Istiophoridae is provided.

Current Ecological Status of Remote Coral Reefs of Clipperton Island, Tropical Eastern Pacific

Clipperton, an uninhabited and remote coral atoll from the Eastern Pacific, is an important steppingstone area that harbors a high marine biodiversity. Despite its biogeographic importance, little information on the ecological status of its coral reefs is available from the last decade. Herein, we characterized the benthic coral community and health status among four different shallow reef-zones (North to South) of Clipperton during the Tara Pacific expedition in 2018. The benthic composition and coverage percentage, as well as occurrence of a pink-spotted coral phenotype (trematodiasis infection) was assessed. Total live coral cover on Clipperton reefs was 66% (55-85%), differing between sites, with massive Porites and branching Pocillopora corals dominating the benthic community with an average 48% (32-66%), and 15% (3-21%), respectively. While Clipperton reefs exhibited significant live coral cover overall, the trematode infection was commonly observed, with a higher occurrence in massive corals (Porites 27%, and Pavona 31%). This observation is possibly related to the combined effects of previously heatwaves, and local inputs of guano-derived nutrients discharged during storms and hurricanes. These results demonstrates that even highly remote reefs supporting high coral cover can be subjected to local and global threats, including but not limited to parasite prevalence, likely in relation to natural disturbances such as thermal stress and tropical cyclones.

Moist Static Potential Vorticity Budget in Tropical Motion Systems

Analyses of simple models of moist tropical motion systems reveal that the column-mean moist static potential vorticity (MSPV) can explain their propagation and growth. The MSPV is akin to the equivalent PV except it uses moist static energy (MSE) instead of the equivalent potential temperature. Examination of an MSPV budget that is scaled for moist off-equatorial synoptic-scale systems reveals that α, the ratio between the vertical gradients of latent and dry static energies, describes the relative contribution of dry and moist advective processes to the evolution of MSPV. Horizontal advection of the moist component of MSPV, a process akin to horizontal MSE advection, governs the evolution of synoptic-scale systems in regions of high humidity. On the other hand, horizontal advection of dry PV predominates in a dry atmosphere. Derivation of a “moist static” wave activity density budget reveals that α also describes the relative importance of moist and dry processes to wave activity amplification and decay. Linear regression analysis of the MSPV budget in eastern Pacific easterly waves shows that the MSPV anomalies originate over the eastern Caribbean and propagate westward due to dry PV advection. They are amplified by the fluxes of the moist component of MSPV over the Caribbean sea and over the eastern Pacific from 105-130°W, underscoring the importance of moist processes in these waves. On the other hand, dry PV convergence amplifies the waves from 90-100°W, likely as a result of the barotropic energy conversions that occur in this region.