A white humpback whale (Megaptera novaeangliae) in the Atlantic Ocean, Svalbard, Norway, August 2012

A white humpback whale (Megaptera novaeangliae) was observed on several occasions off Svalbard, Norway, during August 2012. The animal was completely white, except for a few small dark patches on the ventral side of its fluke. The baleen plates were light-coloured, but the animal's eyes had normal (dark) colouration. This latter characteristic indicates that the animal was not an albino; it was a leucistic individual. The animal was a full-sized adult and was engaged in “bubble-feeding”, together with 15–20 other humpback whales, each time it was seen. Subsequent to these sightings, polling of the marine mammal science community has resulted in the discovery of two other observations of white humpback whales in the Barents Sea area, one in 2004 and another in 2006; in both cases the observed individuals were adult animals. It is likely that all of these sightings are of the same individual, but there is no genetic or photographic evidence to confirm this suggestion. The rarity of observations of such white individuals suggests that they are born at very low frequencies or that the ontogenetic survival rates of the colour morph are low

Greenland sharks (Somniosus microcephalus) scavenge offal from minke (Balaenoptera acutorostrata) whaling operations in Svalbard (Norway)

Minke whale (Balaenoptera acutorostrata) tissue (mainly blubber) was found in the gastrointestinal tracks of Greenland sharks (Somniosus microcephalus) collected in Kongsfjorden, Svalbard, Norway. In order to determine whether the sharks were actively hunting the whales, finding naturally dead whales or consuming offal from whaling, we checked the genetic identity of the whale tissue found in the sharks against the DNA register for minke whales taken in Norwegian whaling operations. All of the minke whale samples from the sharks that had DNA of sufficient quality to perform individual identifications were traceable to the whaling DNA register. During whaling operations, the blubber is stripped from the carcass and thrown overboard. The blubber strips float on the surface and are available for surface-feeding predators. This study revealed that Greenland sharks are scavenging this material; additionally, it demonstrates the capacity of this ‘benthic-feeding’ shark to utilize the whole water column for foraging

Seagrass ecosystem multifunctionality under the rise of a flagship marine megaherbivore

Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems. We assessed the effects of experimentally simulated grazing intensity scenarios on ecosystem functions and multifunctionality in a tropical Caribbean seagrass ecosystem. As a model, we selected a key marine megaherbivore, the green turtle, whose ecological role is rapidly unfolding in numerous foraging areas where populations are recovering through conservation after centuries of decline, with an increase in recorded overgrazing episodes. To quantify the effects, we employed a novel integrated index of seagrass ecosystem multifunctionality based upon multiple, well-recognized measures of seagrass ecosystem functions that reflect ecosystem services. Experiments revealed that intermediate turtle grazing resulted in the highest rates of nutrient cycling and carbon storage, while sediment stabilization, decomposition rates, epifauna richness, and fish biomass are highest in the absence of turtle grazing. In contrast, intense grazing resulted in disproportionally large effects on ecosystem functions and a collapse of multifunctionality. These results imply that (i) the return of a megaherbivore can exert strong effects on coastal ecosystem functions and multifunctionality, (ii) conservation efforts that are skewed toward megaherbivores, but ignore their key drivers like predators or habitat, will likely result in overgrazing-induced loss of multifunctionality, and (iii) the multifunctionality index shows great potential as a quantitative tool to assess ecosystem performance. Considerable and rapid alterations in megaherbivore abundance (both through extinction and conservation) cause an imbalance in ecosystem functioning and substantially alter or even compromise ecosystem services that help to negate global change effects. An integrative ecosystem approach in environmental management is urgently required to protect and enhance ecosystem multifunctionality

Megaherbivores may impact expansion of invasive seagrass in the Caribbean

Abstract of the manuscript to which this dataset belongs to: "1. Our knowledge of the functional role of large herbivores is rapidly expanding, and the impact of grazing on species co-existence and non-native species expansion has been studied across ecosystems. However, experimental data on large grazer impacts on plant invasion in aquatic ecosystems are lacking. 2. Since its introduction in 2002, the seagrass species Halophila stipulacea has rapidly expanded across the Eastern Caribbean, forming dense meadows in green turtle (Chelonia mydas) foraging areas. We investigate the changes in seagrass species co-existence and the impacts of leaf grazing by green turtles on non-native seagrass expansion in Lac Bay (Bonaire, Caribbean Netherlands). 3. Green turtle grazing behavior changed after the introduction of non-native seagrass to Lac Bay in 2010. Field observations, together with time-lapse satellite images over the last four decades, showed initiation of new grazing patches (65 ha, an increase of 72%). The sharp border between grazed and ungrazed seagrass patches moved in the direction of shallower areas with native seagrass species that had previously (1970-2010) been ungrazed. Green turtles deployed with Fastloc-GPS transmitters confirmed high site fidelity to these newly cropped patches. In addition, cafeteria experiments indicated selective grazing by green turtles on native species. These native seagrass species had significantly higher nutritional values compared to the non native species. In parallel, exclosure-experiments showed that non-native seagrass expanded more rapidly in grazed canopies compared to ungrazed canopies. Finally, in six years from 2011-2017, H. stipulacea underwent a significant expansion, invading 20 of 49 fixed monitoring locations in Lac Bay, increasing from 6% to 20% in total occurrence. During the same period, native seagrass Thalassia testudinum occurrence decreased by 33%. 4. Synthesis. Our results provide first-time evidence that H. stipulacea can rapidly colonize and replace native seagrasses in the Caribbean and add a mechanistic explanation for this invasiveness. We conclude that green turtle leaf grazing may modify the rate and spatial extent of this invasive species’ expansion, due to grazing preferences, and increased space for settlement. This work shows how large herbivores play an important but unrecognized role in species co-existence and plant invasions of aquatic ecosystems.

North Atlantic humpback whale abundance and rate of increase four decades after protection from whaling

Humpback whales Megaptera novaeangliae in the North Atlantic Ocean were severely depleted by exploitation. With legal protection since 1955, substantial recovery is likely to have occurred, but information on abundance and rates of increase has been limited. We present an assessment of humpback whale abundance in the North Atlantic Ocean based upon capturerecapture estimates using naturally marked individuals. These data result from a long-term collaborative effort combining large-scale dedicated projects and incidental data collection, leading to extensive geographical coverage. The application of robust statistical techniques produces estimates of greater accuracy and precision than has previously been possible. Abundance estimates ranging from 5930 to 12 580 individuals, with coefficients of variation (CVs) from 0.07 to 0.39, were calculated for the West Indies breeding population using data from 1979 to 1993. The most precise estimate for the West Indies breeding population is 10 752 (CV = 0.068) for 1992 and 1993. Due to application of new analytical methods, these estimates are larger and more precise than those previously published from similar time periods. The average rate of increase for the West Indies breeding population over a 14 yr period was estimated to be 0.031 (SE = 0.005). The best available estimate for the entire North Atlantic population of humpback whales is 11 570 (95% CI 10 290 to 13 390) based upon samples from 1992 and 1993. However, this estimate may be biased downwards to an unknown extent due to heterogeneity in capture probabilities that do not influence the West Indies estimates