Marine Biology最新文献

Abstract

Marine top predators are expected to adjust their foraging behaviour at multiple time scales concomitantly with changes in forage fish availability. Rhinoceros auklets Cerorhinca monocerata rearing chicks at Teuri Island, Japan Sea, fed on anchovy Engraulis japonicus in 2012 and 2013 (anchovy regime) but switched to sand lance Ammodytes spp in 2019 and 2020 (sand lance regime). Here, we studied their at-sea behaviour using the GPS locations of 33 birds and the depth-acceleration records of 26 birds, and compared their foraging behaviour between these prey regimes. At the trip scale, auklets used offshore waters (> 50 m sea depth) and coastal waters in the anchovy regime but used mainland coastal waters (< 50 m sea depth) in the sand lance regime. In the sand lance regime, the birds also conducted more overnight 2- to 4-day trips in 2020 and spent more time flying during 1-day trips as they fed in further areas compared to the anchovy regime. At the dive scale, auklets frequently dove to both < 5 m and 20–30 m depths in the anchovy regime but mainly to < 5 m depth in the sand lance regime. Within each dive, auklets showed a greater number of fast/strong wing stroke events in the anchovy regime than in the sand lance regime. These changes in auklet behaviour reflected the different habitats, depth distribution, and swim speed of the targeted prey species. Our study shows the behavioural flexibility of a wing-propelled flying-diving seabird in response to the inter-annual shifts in the dominant forage fish community. It also indicates the ecological constraints on the mechanisms determining nest productivity in this day-foraging/night-provisioning seabird.

Niche theory predicts that similar species cannot occupy the same geographical space when resources are limited. Sympatric seabirds, such as auks, are ideal models for investigating niche differentiation because they share life history traits and form breeding colonies that rely on common prey items. Auk differentiation may be driven by variations in body mass and wing size, diving capacity, and visual acuity leading each species to forage at different distances, depths, or times of day, respectively. However, previous auk studies have produced diverse results, leaving us with an incomplete understanding of their foraging differentiation across spatial, environmental, and temporal dimensions. In 2021, we tested niche differences at the Mingan Archipelago National Park Reserve, Québec, Canada (50°11′ N, 63°13′ W) by utilizing GPS and time and depth recorders to track the positions of breeding Atlantic puffins (Fratercula arctica), razorbills (Alca torda), and common murres (Uria aalge), which were then paired with environmental data. There was high niche overlap in geographical foraging areas, with auk wing size and mass not appearing to influence their foraging distance. Instead, auk foraging was partitioned over different depths and times of day. Although razorbills and puffins generally exploited shallow foraging areas, puffin foraging activity occurred in deeper waters and at different times of day than razorbills. Murres foraged in the deepest benthic areas and were the only species to forage at night. Our study therefore suggests that auks could be facilitating their coexistence by exhibiting temporal and spatial differences in their foraging behaviours and locations.

Abstract

Slowly sinking small particles in surface seawater are proven to be one of the major contributors to the mesopelagic carbon flux. Phytoplankton can respond rapidly to changes in the marine environment, so assessing the efficiency of their downward export can better constrain the relationship between carbon biomass and sinking fluxes. Here, we measured the sinking rates of individual phytoplankton (φ_indiv) after being subjected to Luzon cold eddy (LCE), warm eddy (WE) and spring warm pool (SWP), and explored the main influencing factors affecting cell sinking. The φ_indiv in the euphotic zone of the central South China Sea (ceSCS) was measured using the SETCOL method during the inter-monsoon period in April 2017. Diatoms (mainly rod-shaped) were sinking faster under the influence of SWP, with the highest carbon fluxes in the surface layer; WE leading to slow sinking of dinoflagellates, rapid sinking of cyanobacteria and a significant reduction in the number of phytoplankton species; diatoms sinking slowly due to the LCE. The φ_indiv of cylinder-shaped and rhombus-shaped cells in diatoms and fusiform-shaped and ellipsoid-shaped cells in dinoflagellates were significantly modulated by cell size. The setae structure of Chaetoceros can modulate the sinking behavior well in different environments. Our results indicate that in the open ocean, the shape and size of cells, the unique ecological niches of different species, and the original localization of cells are essential for the modulation of sinking.

Quantitative data on cephalopods collected in ten multidisciplinary surveys (20–2000 m) between 2004 and 2012, together with original oceanographic and satellite data, were analyzed using multivariate techniques. Statistical analyses were based on presence–absence matrices by species and hydrological variable indices. The results show that cephalopods are distributed in two main zoogeographical groups separated by latitude: “Temperate water” and “Tropical water” clusters. They extended by temperate and tropical regions, separated by a geographical boundary, Cape Blanc, particularly strong in the case of coastal species between these groups. For the total fauna, we have identified a third particular cephalopods’ cluster, the “Upwelling” cluster (22°–17°N), characterized by a higher diversity and dominance of oceanic cephalopods. This is proposed as a new zoogeographical region that would coincide with the area of greatest productivity, intensity and permanence throughout the year of the canary current upwelling, confined between the north of Cape Blanc and the south of Mauritania. The results confirm the strong relationship between the three zoogeographical regions (temperate, tropical, and upwelling) and certain water bodies that characterize the regional hydrology. This paper deepens into the zoogeography of the cephalopods from Northwest Africa (Central-Eastern Atlantic), providing a new, more detailed insight into the region and its boundaries in relation to the oceanography.

The number of individuals to be sampled is a key element in the sampling design of any study as it directly affects the estimations and inferences made. Additionally, in cases where several replicates per individual can be taken, it is important to define how the sampling effort will be distributed between the intraindividual and interindividual components (within and between individuals, respectively). Determining how samples should be distributed among these components can help optimize the available resources and reduce bias in the estimations. To study population trophic diversity, the total niche width (TNW) is usually estimated, which is an approximation of resource diversity at the population level. TNW is the sum of the resource diversity consumed at the intraindividual (replicates) and interindividual (individuals) level. In this study, the effect of prioritizing the number of individuals or the number of replicates on the accuracy and precision of TNW estimations was tested. Multiple isotopic (δ¹³C and δ¹⁵N) values per individual in populations with different degree of individual specialization were simulated. Then, isotopic data from natural populations within the same species (available published studies) were used to assess the results obtained with simulated data. It was found that TNW estimations were more accurate and precise when prioritizing the number of individuals over the replicates, along the entire individual gradient of trophic specialization. Therefore, it is advisable to prioritizing the number of individuals. This methodological contribution should be considered in future studies that use repeated measures of isotopic data to estimate TNW.

Non-indigenous species (NIS) establish and thrive on floating artificial substrata along mid-latitude shores, which might serve as propagule reservoirs and stepping stones for their dispersal. However, often, the NIS are not able to colonize the adjacent seafloor, where high predation pressure by benthic predators might inhibit them. To test this hypothesis, we quantified and compared consumption rates of standardized bait (squidpops) in four water depth zones (sea surface, sub-surface, midwaters, seafloor) in five representative regions in the Southeast Pacific, covering oceanic Rapa Nui (Easter Island; 27°S, 109°W; November 2022) as well as the Chilean continental coast (29–41°S, 71–73°W; March–June 2022). We found a strong overall effect of water zonation, with significant bait consumption being limited to the seafloor and occurring only sporadically in other depth zones. Consumption frequencies also differed between experimental regions but were not influenced by latitude or mean sea surface temperature. An analogous experiment with the NIS Ciona robusta, conducted at one sampling site, showed that the occurrence or absence of predation per site and water depth zone, but not the exact consumption rates, concurred between both bait types. Our results confirm that predation in SE Pacific temperate shallow waters mainly depends on benthic predators that cannot reach higher zones of the water column. These findings have far-reaching implications, as they indicate that predation rates in mid-latitude systems might be underestimated through commonly used water column-based experiments. For a comprehensive estimation of predation pressure in a given system, future studies should consider differences between vertical water zones.

Worldwide, seabird populations are facing significant declines due to various threats, making them valuable bioindicators of marine ecosystem changes. Understanding their foraging behavior and identifying crucial foraging areas (FAs) is essential for their conservation. In this study, the focus was on Olrog’s gull (Larus atlanticus), a near-threatened species endemic to the Atlantic coast of Argentina, Uruguay, and southern Brazil. The objectives were to assess the distribution of FAs and home ranges of Olrog’s gull and to evaluate the overlap between FAs and protected areas (PAs) in the Bahía Blanca Estuary (BBE), Argentina. Global positioning system (GPS) tracking and dynamic Brownian bridge movement models (dBBMM) were used to analyze Olrog’s gull behavior during their breeding season. The results revealed well-defined FAs, with 72% of them located outside PAs, raising concerns about potential threats to the species. Sex-related differences were observed, with females covering longer distances during foraging flights. In addition, several FAs were located near industrial sites, posing health risks due to pollution. This study contributes novel insights into Olrog’s gull foraging ecology, particularly in the most critical breeding area for the species. A dynamic web application was developed to provide rapid access to comprehensive information applicable to conservation actions. These findings underscore the need for enhanced protection of critical FAs, particularly those lying outside currently PAs.

This research emphasizes the importance of well-informed policy decisions to enhance ongoing conservation initiatives for Olrog’s gull populations and their habitats, particularly in the face of increasing threats posed by human activities.

The right third arm of the male octopus is the hectocotylized arm. This arm is modified by anatomy specialized to hold and transfer sperm packets to the female, and lacks suckers at the distal end. Male octopus may be distinguished by the skilled eye from their habit of holding their hectocotylus closer to their body in a protective manner, although this observation has never been described quantitatively. We utilized a three-step process of data annotation, pose estimation model training, and model inference to show that this common observation is true of Octopus rubescens. In 2338 images, the eyes, mantle tip, and arm tips of two male (n = 1152) and three female (n = 1085) octopuses were annotated by an experimenter. These images were then used to train a DeepLabCut pose estimation model which achieved a RMSE of 1.78 cm. This model was then used to annotate 11.4 h (n = 408,985 images) of four female and eight male octopuses moving across the middle of a large aquarium. We then compared the human annotated data, and the model inference data separately. In both datasets we compared the arm-tip-to-eye centered point distances, as well as the octopus centric arm tip 90% kernel density estimation area. In both the training dataset and the model inference datasets we found common results. Male O. rubescens hold their third to the right arm closer to their body than all seven other arms while the females do not. Further, in both males and females, the rear arm pairs operate closer to the body than the front arm pairs. Despite their anatomical similarity and potential redundancy, these results indicates functional differences in arm use by octopuses.

Abstract

Thermal conditions in the nest affect the development of sea turtle clutches, with high temperatures potentially reducing reproductive success and the quality of hatchlings. In a warming climate, increasing temperatures could become a threat to sea turtles in many locations. This has prompted the implementation or recommendation of climate mitigation strategies in nests that incubate in hatchery conditions. Here, olive ridley turtle (Lepidochelys olivacea) clutches relocated to a beach hatchery in Playa Grande, Costa Rica (10° 20 N, 85° 51 W) were used to study the effect of temperature on hatching success and hatchling size. Data from 5 nesting seasons (2017/18 to 2022/23, excluding 2020/21) were tested to determine the effect of mean incubation temperature by thirds of development, as well as over the whole incubation period. Hatching success was lower at low and high temperatures and higher at intermediate ones during the second and last thirds of development. Optimal mean temperature ranges were 29–32 °C and 32–35 °C across the second and last thirds of development respectively, and 30–32.5 °C during the whole incubation period. There was no statistically significant effect of temperature on hatching success during the first third of development. High temperature resulted in shorter carapace width but did not statistically affect mass or carapace length. The temperature effect on carapace width occurred in all thirds of development. Studying temperature effects on target species nests at the local level, throughout incubation, and over multiple years is important for applying climate mitigation strategies properly.

In order to address lack of data regarding coastal carbon budgets, we estimated the annual metabolic carbon budget of an intertidal rocky reef macroalgal community during emersion. This budget is based on direct in situ measurements during emersion and establishes the seasonal variations of the photosynthetic parameters of such a community. CO₂ fluxes were measured hourly to study the response of community gross primary productivity (GPP) to irradiance and the variation of GPP and community respiration (CR) over the emersion period at different times of the year. These were combined together with existing monthly measures of GPP and CR hourly rates to model the variations of these fluxes as a function of irradiance and the tidal cycle throughout an entire calendar year. Daily, monthly and annual values of GPP, CR and net primary productivity (NPP) were calculated with a relatively low sensitivity to any of the parameters used. While GPP fluxes show comparable orders of magnitude to those measured in other systems, higher CR fluxes lead to a heterotrophic system during emersion, both under measured (NPP = −299 gC m⁻² year⁻¹) and theoretical irradiances (NPP = −119 gC m⁻² year⁻¹). This heterotrophy is directly linked to the light availability, varying according to combined daily, tidal and seasonal cycles, and to temperature at the seasonal scale. Measurements performed in situ at the community scale integrated interactions that are otherwise absent at the individual scale. This gives access to aspects of the functioning that cannot be otherwise identified.