Search

Marine debris pollution poses a significant global threat to biodiversity, with plastics being the primary debris type found in oceans due to their low-cost production and high demand worldwide. Microplastics (MPs, <5 mm in size) are highly bioavailable to a wide range of marine taxa, including marine mammals, through direct and indirect ingestion routes (i.e., trophic transfer). Recently, MP pollution has been detected on the Galapagos Marine Reserve, so in this study we developed a baseline framework for MP pollution in the Galapagos sea lion (GSL, Zalophus wollebaeki) through scat-based analysis. We collected 180 GSL scat samples from the southeast region following strict quality assurance/quality control protocols to detect, quantify and characterize physical-chemical properties of MPs through visual observations and μFT-IR spectroscopy. We recovered 81 MPs of varying sizes and colors in 37 % of samples (n = 66/180), consisting mostly of fibers (69 %, x¯ = 0.31 ± 0.57 particles scat -1 ). The number of particles per gram of sample wet weight ranged from 0.02 to 0.22 (x¯ = 0.04 ± 0.05 particles scat wet g -1 ). El Malecón and Punta Pitt rookeries at San Cristobal Island had the highest number of MPs (x¯ = 0.67 ± 0.51 and 0.43 ± 0.41 particles scat -1 , respectively), and blue-colored particles were the most common in all samples. We identified eleven polymers in 46 particles, consisting mostly of polypropylene-polyethylene copolymer, polypropylene, cellulose, polyethylene, and polyvinyl chloride. The textile, fishing, and packaging industries are likely significant sources of microfibers into this insular ecosystem. Our results suggest that the GSL is exposed to MPs due to anthropogenic contamination that is subsequently transferred through trophic processes. These findings provide an important baseline framework and insights for future research on MP pollution in the region, as well as for management actions that will contribute to the long-term conservation of the GSL., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: The Galapagos sea lion, Zalophus wollebaeki , is an endemic and endangered otariid, which is considered as a sentinel species of ecosystem dynamics in the Galapagos archipelago. Mitochondrial DNA is an important tool in phylogenetic and population genetic inference. In this work we use Illumina sequencing to complement the mitogenomic resources for Zalophus genus-the other two species employed Sanger sequencing-by a complete mitochondrial genome and a molecular clock of this species, which is not present in any case., Materials and Methods: We used DNA obtained from a fresh scat sample of a Galapagos sea lion and shotgun-sequenced it on the Illumina NextSeq platform. The obtained raw reads were processed using the GetOrganelle software to filter the mitochondrial Zalophus DNA reads (∼16% survive the filtration), assemble them, and set up a molecular clock., Results: From the obtained 3,511,116 raw reads, we were able to assemble a full mitogenome of a length of 16,676 bp, consisting of 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNA), and two ribosomal RNAs (rRNA). A time-calibrated phylogeny confirmed the phylogenetic position of Z. wollebaeki in a clade with Z. californianus , and Z. japonicus , and sister to Z. californianus ; as well as establishing the divergence time for Z. wollebaeki 0.65 million years ago. Our study illustrates the possibility of seamlessly sequencing full mitochondrial genomes from fresh scat samples of marine mammals., Competing Interests: The authors declare there are no competing interests., (©2023 Asadobay et al.)

Tropical ecosystems are challenging for pinnipeds due to fluctuating food availability. According to previous research, the Galapagos sea lion (GSL, Zalophus wollebaeki) adopts trophic flexibility to face such conditions. However, this hypothesis comes from studies using traditional methods (hard‐parts analysis of scat and isotopic analysis from tissue). We studied the diet of five rookeries in the southeastern Galapagos bioregion (which harbors the highest GSL density), via DNA‐metabarcoding of scat samples. The DNA‐metabarcoding approach may identify consumed prey with a higher taxonomic resolution than isotopic analysis, while not depending on hard‐parts remaining through digestion. Our study included five different rookeries to look for evidence of trophic flexibility at the bioregional level. We detected 98 prey OTUs (124 scats), mostly assigned to bony‐fish taxa; we identified novel prey items, including a shark, rays, and several deep‐sea fish. Our data supported the trophic flexibility of GSL throughout the studied bioregion since different individuals from the same rookery consumed prey coming from different habitats and trophic levels. Significant diet differentiations were found among rookeries, particularly between Punta Pitt and Santa Fe. Punta Pitt rookery, with a more pronounced bathymetry and lower productivity, was distinguished by a high trophic level and consumption of a high proportion of deep‐sea prey; meanwhile, Santa Fe, located in more productive, shallow waters over the shelf, consumed a high proportion of epipelagic planktivorous fish. Geographic location and heterogeneous bathymetry of El Malecon, Española, and Floreana rookeries would allow the animals therein to access both, epipelagic prey over the shelf, and deep‐sea prey out of the shelf; this would lead to a higher prey richness and diet variability there. These findings provide evidence of GSL adopting a trophic flexibility to tune their diets to different ecological contexts. This strategy would be crucial for this endangered species to overcome the challenges faced in a habitat with fluctuating foraging conditions. [ABSTRACT FROM AUTHOR]

The skull often reveals adaptation to ecological and environmental influences. Food availability affects the somatic growth of otariids, and population abundance can influence male intrasexual competition. We hypothesized there would be regional differences between Galapagos sea lion (GSL, Zalophus wollebaeki) rookeries as a result of variance in ecosystem metrics and population abundance. We used skull measures related to individual size and aggressiveness. We analyzed 19 linear measures for size and 15 for aggressiveness taken on 49 adult male skulls of GSL collected in four bioregions of the archipelago. Nine skull measures had a significant effect on individual clustering into bioregions (P < 0.001). The most discriminating measures were snout length, supraorbital process width, nasal length, and canine width. We found a significant relationship between skull grouping patterns and chlorophyll-α levels (proxy marine productivity and body growth) and GSL population abundance (proxy of agonistic behavior) of each bioregion, as well as with the interaction between both variables (P < 0.001). Our results suggest significant regional differences in GSL skull morphometry, which could be associated with resource availability and level of male intrasexual competition in the archipelago. This information is important for understanding the life history of this species. El cráneo es útil para mostrar los efectos de adaptación de las especies a diferentes influencias ecológicas y ambientales. Basados en que la disponibilidad de alimento afecta al crecimiento somático de los otáridos y que la abundancia poblacional puede afectar la competencia intrasexual en machos, pensamos que podría existir diferencias regionales entre las colonias del lobo marino de Galápagos (LMG, Zalophus wollebaeki) como resultado de la variabilidad ambiental y distintas abundancias poblacionales. Usamos medidas craneales relacionadas con el tamaño del individuo (secciones que definen sólo crecimiento) y la agresividad (áreas de inserción de músculos asociados con su comportamiento antagonista). En este contexto, se analizaron 19 medidas lineales para tamaño y 15 para agresividad tomadas en 49 cráneos de machos adultos de LMG. Con base en información ecológica, se dividió el archipiélago en cuatro biorregiones: norte (n = 7), oeste (n = 16), centro (n = 8), y sureste (n = 18). El mejor modelo de análisis discriminante flexible basado en el criterio Lambda de Wilk (P < 0,001), contenía nueve de las medidas del cráneo que tuvieron un efecto significativo en la agrupación individual de las biorregiones (P < 0.001). Las medidas más discriminatorias fueron la longitud del hocico: SL, ancho proceso supraorbital: SPW, longitud nasal: NL y ancho canino: CW (Lambda de Wilk P < 0.3). Encontramos una asociación significativa entre los patrones de agrupamiento del cráneo con los niveles de clorofila-α (proxy de productividad marina y crecimiento corporal) y la abundancia de población GSL (proxy de comportamiento agonista) de cada biorregión, así como con la interacción entre ambas variables (modelo lineal). Nuestros resultados sugieren diferencias regionales en la morfometría del LMG, que podrían estar asociadas con una distinta disponibilidad de recursos y nivel de competencia intrasexual en machos en el archipiélago. Esta información es relevante para entender la historia de vida de esta especie, así como sus oportunidades y amenazas. [ABSTRACT FROM AUTHOR]

The Galapagos sea lion (Zalophus wollebaeki) is one of the few pinnipeds adapted to tropical ecosystems. This adaptation exposes this species to productivity fluctuations associated with oceanographic events, such as ENSO, which has generated a significant population decline during recent decades. This decline represents a considerable challenge for the species, especially for females who invest a large part of their energy in the maintenance of their pups. A comparative analysis of the isotopic signals of whisker samples taken from Z. wollebaeki pups was performed to understand the foraging ecology of their mothers during the pre- and post-partum stages. A significant relationship was observed between the whisker size and the total length of the pups (r s = 0.96, P < 0.05), which enabled a date to be provided for each whisker fragment and for it to be assigned to a specific month. Model-based clustering of isotope ratios identified two distinct clusters in both stages, where the level of uncertainty of the grouping was lower than 40%. The δ 13C and δ 15N values among clusters within each stage defined differences in the feeding zones and in the trophic levels in both groups (P < 0.01). No significant difference was found in the δ 13C values between the pre- and post-partum stages, but a significant decrease was observed in the δ 15N values in the post-partum period (P = 0.01). There was no correlation of the monthly isotopic values with the superficial sea temperature (SST) and chlorophyll- a (Chl- a); however, the low δ 13C values observed during October 2015 matched with an increase in SST and a decrease of Chl- a in the region. Thus, through the analysis of pup samples, we successfully obtained results that give us an insight into the trophic ecology and metabolic processes behind the isotopic signatures of Z. wollebaeki females. [ABSTRACT FROM AUTHOR]