Ocean currents have many profound impacts on marine life, moving not only animals and plants around the ocean but also redistributing heat and nutrients. While some of these impacts have been well ...known for many decades, there have been major recent developments in this area. Biologists are increasingly collaborating with physical oceanographers. At the same time, methods to accurately predict ocean currents and their variability have improved over a broad range of spatial and temporal scales. Emerging from these initiatives is an understanding of how currents impact the connectivity of marine populations, how they influence the migration of strong swimmers, including whales and turtles, and how changing currents, as part of global climate change, may re-shape entire communities.
Graeme Hays introduces the ways in which ocean currents influence marine life.
New frontiers in biologging science Rutz, Christian; Hays, Graeme C.
Biology letters,
06/2009, Volume:
5, Issue:
3
Journal Article, Conference Proceeding
Peer reviewed
Open access
The term 'biologging' refers to the use of miniaturized animal-attached tags for logging and/or relaying of data about an animal's movements, behaviour, physiology and/or environment. Biologging ...technology substantially extends our abilities to observe, and take measurements from, free-ranging, undisturbed subjects, providing much scope for advancing both basic and applied biological research. Here, we review highlights from the third international conference on biologging science, which was held in California, USA, from 1 to 5 September 2008. Over the last few years, considerable progress has been made with a range of recording technologies as well as with the management, visualization, integration and analysis of increasingly large and complex biologging datasets. Researchers use these techniques to study animal biology with an unprecedented level of detail and across the full range of ecological scales-from the split-second decision making of individuals to the long-term dynamics of populations, and even entire communities. We conclude our report by suggesting some directions for future research.
Ontogeny of long distance migration Scott, Rebecca; Marsh, Robert; Hays, Graeme C
Ecology,
October 2014, Volume:
95, Issue:
10
Journal Article
Peer reviewed
Open access
The movements of some long-distance migrants are driven by innate compass headings that they follow on their first migrations (e.g., some birds and insects), while the movements of other first-time ...migrants are learned by following more experienced conspecifics (e.g., baleen whales). However, the overall roles of innate, learned, and social behaviors in driving migration goals in many taxa are poorly understood. To look for evidence of whether migration routes are innate or learned for sea turtles, here for 42 sites around the world we compare the migration routes of >400 satellite-tracked adults of multiple species of sea turtle with ∼45 000 Lagrangian hatchling turtle drift scenarios. In so doing, we show that the migration routes of adult turtles are strongly related to hatchling drift patterns, implying that adult migration goals are learned through their past experiences dispersing with ocean currents. The diverse migration destinations of adults consistently reflected the diversity in sites they would have encountered as drifting hatchlings. Our findings reveal how a simple mechanism, juvenile passive drift, can explain the ontogeny of some of the longest migrations in the animal kingdom and ensure that adults find suitable foraging sites.
The response of marine plankton to climate change is of critical importance to the oceanic food web and fish stocks. We use a 60-year ocean basin-wide data set comprising >148,000 samples to reveal ...huge differences in range changes associated with climate change across 35 plankton taxa. While the range of dinoflagellates and copepods tended to closely track the velocity of climate change (the rate of isotherm movement), the range of the diatoms moved much more slowly. Differences in range shifts were up to 900 km in a recent warming period, with average velocities of range movement between 7 km per decade northwards for taxa exhibiting niche plasticity and 99 km per decade for taxa exhibiting niche conservatism. The differing responses of taxa to global warming will cause spatial restructuring of the plankton ecosystem with likely consequences for grazing pressures on phytoplankton and hence for biogeochemical cycling, higher trophic levels and biodiversity.
Patterns of animal movement associated with foraging lie at the heart of many ecological studies and often animals face decisions of staying in an environment they know versus relocating to new ...sites.
The lack of knowledge of new foraging sites means there is risk associated with a decision to relocate (e.g. poor foraging) as well as a potential benefit (e.g. improved foraging).
Using a unique long‐term satellite tracking dataset for several sea turtle species, combined with capture–mark–recapture data extending over 50 years, we show how, across species, individuals generally maintain tight fidelity to specific foraging sites after extended (up to almost 10,000 km) migration to and from distant breeding sites as well as across many decades.
Migrating individuals often travelled through suitable foraging areas en route to their ‘home’ site and so extended their journeys to maintain foraging site fidelity.
We explore the likely mechanistic underpinnings of this trait, which is also seen in some migrating birds, and suggest that individuals will forgo areas of suitable forage encountered en route during migration when they have poor knowledge of the long‐term suitability of those sites, making relocation to those sites risky.
Using satellite tracking in the western Indian Ocean and northern Australia, the authors show that adult green turtles have fidelity to small foraging areas that may be 1,000s of km from their nesting beach. Individuals often forgo suitable foraging areas encountered during migration, probably because relocation to those sites is risky.
For species with temperature-dependent sex determination (TSD) there is the fear that rising temperatures may lead to single-sex populations and population extinction. We show that for sea turtles, a ...major group exhibiting TSD, these concerns are currently unfounded but may become important under extreme climate warming scenarios. We show how highly female-biased sex ratios in developing eggs translate into much more balanced operational sex ratios so that adult male numbers in populations around the world are unlikely to be limiting. Rather than reducing population viability, female-biased offspring sex ratios may, to some extent, help population growth by increasing the number of breeding females and hence egg production. For rookeries across the world (n = 75 sites for seven species), we show that extreme female-biased hatchling sex ratios do not compromise population size and are the norm, with a tendency for populations to maximize the number of female hatchlings. Only at extremely high incubation temperature does high mortality within developing clutches threaten sea turtles. Our work shows how TSD itself is a robust strategy up to a point, but eventually high mortality and female-only hatchling production will cause extinction if incubation conditions warm considerably in the future.
1. Some animals migrate huge distances in search of resources with locomotory mode (flying/swimming/walking) thought to drive the upper ceilings on migration distance. Yet in cross-taxa comparisons, ...upper ceilings on migration distance have been ignored for one important group, sea turtles. 2. Using migration distances recorded for 407 adult and 4715 juvenile sea turtles across five species, we show that for adult cheloniid turtles, the upper ceiling on species migration distances between breeding and foraging habitats (1050—2850 km across species) is similar to that predicted for equivalent-sized marine mammals and fish. 3. In contrast, by feeding in the open ocean, adult leatherback turtles (Dermochelys coriacea) and juveniles of all turtle species can travel around 12000 km from their natal regions, travelling across the widest ocean basins. For juvenile turtles, this puts their maximum migration distances well beyond those expected for equivalent-sized marine mammals and fish, but not those found in some similar sized birds. 4. Post-hatchling turtles perform these long-distance migrations to juvenile foraging sites only once in their lifetime, while adult turtles return to their breeding sites every few (generally ≥2) years. Our results highlight the important roles migration periodicity and foraging mode can play in driving the longest migrations, and the implications for Marine Protected Area planning are considered in terms of sea turtle conservation.
Estimating the absolute number of individuals in populations and their fecundity is central to understanding the ecosystem role of species and their population dynamics as well as allowing informed ...conservation management for endangered species. Estimates of abundance and fecundity are often difficult to obtain for rare or cryptic species. Yet, in addition, here we show for a charismatic group, sea turtles, that are neither cryptic nor rare and whose nesting is easy to observe, that the traditional approach of direct observations of nesting has likely led to a gross overestimation of the number of individuals in populations and underestimation of their fecundity. We use high-resolution GPS satellite tags to track female green turtles throughout their nesting season in the Chagos Archipelago (Indian Ocean) and assess when and where they nested. For individual turtles, nest locations were often spread over several tens of kilometres of coastline. Assessed by satellite observations, a mean of 6.0 clutches (range 2–9, s.d. = 2.2) was laid by individuals, about twice as many as previously assumed, a finding also reported in other species and ocean basins. Taken together, these findings suggest that the actual number of nesting turtles may be almost 50% less than previously assumed.
Issue Title: Migrations and Dispersal of Marine Organisms Diel vertical migration (DVM) by zooplankton is a universal feature in all the World's oceans, as well as being common in freshwater ...environments. The normal pattern involves movement from shallow depths at night to greater depths during the day. For many herbivorous and omnivorous mesozooplankton that feed predominantly near the surface on phytoplankton and microzooplankton, minimising the risk of predation from fish seems to be the ultimate factor behind DVM. These migrants appear to use deep water as a dark daytime refuge where their probability of being detected and eaten is lower than if they remained near the surface. Associated with these vertical movements of mesozooplankton, predators at higher trophic levels, including invertebrates, fish, marine mammals, birds and reptiles, may modify their behaviour to optimise the exploitation of their vertically migrating prey. Recent advances in biotelemetry promise to allow the interaction between migrating zooplankton and diving air-breathing vertebrates to be explored in far more detail than hitherto.PUBLICATION ABSTRACT
For organisms that fly or swim, movement results from the combined effects of the moving medium — air or water — and the organism's own locomotion. For larger organisms, propulsion contributes ...significantly to progress but the flow usually still provides significant opposition or assistance, or produces lateral displacement (‘drift’). Animals show a range of responses to flows, depending on the direction of the flow relative to their preferred direction, the speed of the flow relative to their own self-propelled speed, the incidence of flows in different directions and the proportion of the journey remaining. We here present a classification of responses based on the direction of the resulting movement relative to flow and preferred direction, which is applicable to a range of taxa and environments. The responses adopted in particular circumstances are related to the organisms' locomotory and sensory capacities and the environmental cues available. Advances in biologging technologies and particle tracking models are now providing a wealth of data, which often demonstrate a striking level of convergence in the strategies that very different animals living in very different environments employ when moving in a flow.
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