Breeding seabirds must balance the energetic demands of feeding themselves and their offspring while coping with the constraints imposed by central-place foraging. As such, foraging strategies and parental care patterns are usually linked. Here, the foraging behavior of the Red-billed Tropicbird (Phaethon aethereus; n = 161) of Peña Blanca Islet, Mexico (19° 06ʹ 11ʺ N, 104° 29ʹ 12ʺ W) during the incubation and chick-rearing (≤ 4 weeks of age) stages was characterized with the aid of GPS loggers. Blood samples from adults and chicks were collected to determine δ15N and δ13C, and parental presence at the nest, meal size, and parent-chick feeding events were recorded. During incubation, parents made long trips offshore to areas far from the colony; however, immediately after their chicks hatched, the parents switched to a bimodal foraging strategy by undertaking both short and long foraging trips. The δ15N values indicated that trophic differences were present between parents and their offspring, with chicks being fed prey enriched in 15N. Parental presence at the nest was greater during early chick-rearing, which was associated with a higher provisioning rate. Parents adopted a strategy in which the parent on nest duty only made short foraging trips to provide for its offspring without leaving it unattended for long periods, while its mate undertook long trips to feed itself. After the early chick-rearing period, the parents gradually reduced the time spent at the nest and increased the time spent foraging, compensating with larger meal sizes for their offspring.Graphical abstract

Cassiopea xamachana is a tropical medusa that lives in symbiosis with dinoflagellate algae, serving as a model organism for symbiotic studies. The symbiosis is necessary for this medusa to complete its life cycle. The symbiotic partners maintain a metabolic exchange of organic molecules that constitute an important source of energy for the animal host, with free organic molecules, like glucose and glycerol, being the primary source. This molecular exchange can be facilitated by cellular internal membrane transport proteins, such as Glucose membrane transporters (GLUTs) and Glycerol transport-like aquaglyceroporins (GLP-like), probably located at the symbiosomal interface. The present study was conducted in October 2021, evaluating the expression of transporter coding genes GLUT3, GLUT8, and GLP9 (two genes) by qPCR under conditions of symbiosis and after the loss of symbionts. Symbiotic medusae donated from Xcaret Park, Mexico (20° 34′ 24.59″ N; -87° 07′ 5.40″ W) were sampled and compared to medusae with an experimental decrease of algal symbionts. In agreement with glucose being an important mobile molecule, our results showed higher transcription levels for glucose transporters GLUT3 and GLUT8 in control compared to bleached medusae. By contrast, bleached medusae showed a higher expression of aquaglyceroporin transporters GLP9-1 and GLP9-2, probably associated with glycerol production after lipid catabolism, to compensate for lower organic carbon levels due to the loss of symbionts. Our results highlight the importance of free carbon molecules transported from symbiont to host and agree with glucose being an energy fuel for this symbiotic association.

Tropical western Atlantic reefs have gradually shifted from being dominated by corals to being mainly covered by macroalgae. The mass-mortality of the sea urchin Diadema antillarum in the 80s and the slow to non-existent recovery exacerbated this shift. Chemical cues associated with these reefs are expected to have shifted too with potential negative effects on larval recruitment, possibly limiting recovery of important species like D. antillarum. In this study, we tested the effects of naturally derived biofilm and macroalgae species native to Caribbean coral reefs on the settlement rate of cultured D. antillarum larvae in two separate experiments. Crustose coralline algae (CCA) were included in both experiments, making it possible to compare settlement rates from both experiments. A biofilm of one week old yielded significantly lower settlement rates compared to two, four, and six weeks old biofilm and the highest settlement rate was found for CCA with over 62% of total larvae. All six tested macroalgae species resulted in settled larvae, with little significant difference between algal species, partly due to a high variation in settlement rates within treatments. Sargassum fluitans induced the highest settlement rate with 33%, which was not significantly different from CCA with 29%. We conclude that dominant macroalgae species likely to be encountered by D. antillarum on shifted reefs are no major constraint to settlement. Our findings increase the understanding of alternative stable state settlement dynamics for a keystone coral reef herbivore.

The health status of cold-water coral reefs on the West African coast was investigated with the main objective of obtaining knowledge of the adaptive capacity of Lophelia pertusa to environmental stressors. Three coral sites were studied, in Northern Morocco, in the Morocco/Mauritania region (both in 2020) and, in the Ghana and Ivory coast region (visited in 2012, 2017, and 2019). Area cover of live colonies, explored through underwater videos, was used as an indicator of reef health and compared with the environmental variables: reef position, depth, water mass, temperature, dissolved oxygen concentration (DO), carbonate chemistry (pH, aragonite saturation (ΩAr), macronutrients and particles (visual). For a broader picture of the adaptations presented by Lophelia our results were compared with reefs in contrasting environments. Off Ghana and Mauritania healthy reefs (i.e., having areas with more than 20 % cover of live colonies) were found to reside at DO concentrations between 1.1 and 1.6 ml L−1, in corrosive waters (pH 7.7 and ΩAr 1.0) with high nutrient concentrations. By contrast, the reefs off the North of Morocco, sitting in well-oxygenated waters with oversaturated ΩAr, had no or few live colonies. Our findings together with data from other studies show that Lophelia has a wide tolerance to hypoxia and acidification, and that in relation to climate change increased temperature and silting could pose more serious threats. These findings highlight the importance of continued studies of Lophelia reefs in contrasting environmental conditions to better understand their adaptation potential to climate change-related stressors.

Environmental DNA (eDNA) analysis is a promising method to monitor marine biodiversity. Examining the capacity of eDNA to provide accurate biodiversity measures in species-rich ecosystems such as coastal waters is a prerequisite for their application in long-term monitoring. Therefore, both underwater visual census (UVC) and eDNA metabarcoding were conducted monthly from June 2018 to May 2019 to investigate sh diversity on the coast of Nodaedo Island in Tongyeong, South Korea. A total of 16,036 individuals were observed by UVC and classi ed into 69 species, with perciform sh being the most dominant (31 species). eDNA metabarcoding detected 68 operational taxonomy units (OTUs) and 738,217 reads, accounting for a total of 18 orders, 42 families, and 68 species. The Gobiidae family was the most dominant taxon, encompassing ve species. The UVC method could detect species that were otherwise not identi ed through eDNA due to the small number of individuals or analytical limitations. eDNA metabarcoding was suitable for detecting smaller species, pelagic species, and those that inhabit microhabitats. Our ndings demonstrated that these two methods can complement each other to gain insights into the structure of the communities of sh that inhabit various coastal environments. eDNA metabarcoding can be applied as a fast and e cient method to conduct surveys on sh species diversity in coastal waters. However, this approach must be further compared with traditional survey methods to validate its applicability as an effective complement to traditional measures.