Global patterns in species richness of pelagic seabirds: the Procellariiformes

Quantitative information on large scale spatial patterns of biodiversity remains poor, especially for pelagic systems. In this paper the regional diversity of procellariiforms is mapped worldwide at the species level. These seabirds do not display a conventional latitudinal gradient of decreasing species richness towards high latitudes, but rather are most speciose between 37° and 59°S in all ocean basins. Based on data for foraging ranges, areas with the highest species richness and the most species with smaller range sizes are all found in the vicinity of New Zealand and its sub-Antarctic islands. In contrast, data for breeding ranges show islands in the southern Indian and Atlantic oceans to have the highest number of breeding species, while these islands and New Zealand have the most species with smaller range sizes. No northern hemisphere regions are amongst the top ten grid cells for foraging and breeding species richness, although Hawaii has the highest species richness of procellariilforms north of the equator. Northern Baja California. Madeira, the Canary islands, and the west coast of South America are all important sites of narrow endemism in the northern hemisphere. High species richness and narrow endemism coincide with areas of significant longline fishing activity in the southern hemisphere. Near-minimum sets based on one and three representations demonstrate that if all procellariiform species are to be retained, large areas of the ocean and almost all breeding sites require conservation.     

Are pelagic seabirds exposed to amnesic shellfish poisoning toxins?

Marine birds have been hypothesized to be underreported victims of harmful algal blooms (HABs). Toxic blooms of Pseudo-nitzschia spp., the primary amnesic toxin producer microalgae, domoic acid (DA) are known to cause massive mortalities of coastal seabirds and marine mammals around the world. However, these fatalities are only detected when birds die nearby the coastline and little is known about possible outbreaks of pelagic seabirds in oceanic areas. Here we aim to understand whether pelagic seabirds are exposed to amnesic shellfish poisoning (ASP) toxins. For this purpose, we tracked pelagic seabirds feeding on small epipelagic fish and squid, reported to be vectors of DA, which are obtained in high productivity zones where intense Pseudo-nitzschia blooms regularly occur. In particular, we tracked Cory’s (Calonectris borealis) and Scopoli’s (C. diomedea) shearwaters breeding in Gran Canaria (Canary Is.) and in Menorca (Balearic Is.) and feeding on the Canary Current region and the Catalonian coast, respectively. We sampled birds for blood at the recovery of the GPS (Global Positioning System) and analyzed it for DA determination by Liquid Chromatography coupled with Tandem Mass Spectrometry (LC–MS/MS). Among the 61 samples analyzed from Gran Canaria, and 87 from Menorca, 31 (50.8%) and 28 (32.2%) from each location presented detectable levels of DA ranging 1.0–10.6 ng mL⁻¹. This work reveals that DA can be detected at variable levels in the blood of ASP-asymptomatic shearwaters and suggests a chronic exposure of shearwaters to DA, highlighting the need for further studies on DA effects. These results are of high relevance due to the vulnerability of these marine birds, which populations are in continuous decline. Since global warming is expected to alter and increase the occurrence of HABs, marine toxins might become an additional stressor for seabirds and exacerbate the already precarious conservation status of many species.     

Kidney lesions in pelagic seabirds with high tissue levels of cadmium and mercury

Light and electron microscopic techniques were employed to examine the kidneys of three species of pelagic seabird which had high tissue cadmium and mercury levels. Direct examination and comparison with the kidneys of cadmium and mercury dosed starlings showed that the seabirds had patchy nephrotoxic kidney lesions. It was suggested that these lesions were due to natural exposure of the animals to high levels of metals, particularly cadmium through their diet. Pathological features included necrosis and degeneration of the proximal tubular epithelium together with the direct observation of obstruction of the more distal neprhon segments by necrotic cellular debris. Abnormalities of the glomerular podocytes and Bowman's capsule cells were also observed. There was a high degree of similarity between the type and distribution of kidney lesions in the seabirds and the laboratory metal dosed starlings. The significance of this kidney damage and its possible effects on the birds survival prospects are discussed.     

The largely neglected ecological role of oceanic pelagic fungi

Most investigations into ocean ecology and biogeochemistry have tended to focus on marine bacteria, archaea, and protists, while pelagic fungi (mycoplankton) have traditionally been neglected and considered to reside only in association with benthic solid substrates. Nevertheless, recent studies have revealed that pelagic fungi are distributed ubiquitously throughout the water column in every ocean basin and play an active role in the degradation of organic matter and the cycling of nutrients. We review the current status of knowledge on the ecology of mycoplankton and highlight knowledge gaps and challenges. These findings underscore the need to recognize this neglected kingdom as significant contributors to the organic matter cycling and ecology of the oceans.     

Unexpected variation in lignin.

Recent studies on mutant and transgenic plants indicate that lignification may be far more flexible than previously realized. Pines with a mutation affecting the biosynthesis of the major lignin precursor, coniferyl alcohol, show a high level of an unusual subunit, dihydroconiferyl alcohol. These results argue in favor of an increased potential for genetic modification of lignin and indicate that our knowledge of the biosynthesis of lignin is far from complete.     

Increased oceanic microplastic debris enhances oviposition in an endemic pelagic insect

Plastic pollution in the form of small particles (diameter less than 5 mm)-termed 'microplastic'-has been observed in many parts of the world ocean. They are known to interact with biota on the individual level, e.g. through ingestion, but their population-level impacts are largely unknown. One potential mechanism for microplastic-induced alteration of pelagic ecosystems is through the introduction of hard-substrate habitat to ecosystems where it is naturally rare. Here, we show that microplastic concentrations in the North Pacific Subtropical Gyre (NPSG) have increased by two orders of magnitude in the past four decades, and that this increase has released the pelagic insect Halobates sericeus from substrate limitation for oviposition. High concentrations of microplastic in the NPSG resulted in a positive correlation between H. sericeus and microplastic, and an overall increase in H. sericeus egg densities. Predation on H. sericeus eggs and recent hatchlings may facilitate the transfer of energy between pelagic- and substrate-associated assemblages. The dynamics of hard-substrate-associated organisms may be important to understanding the ecological impacts of oceanic microplastic pollution.     

Quantifying habitat use in satellite-tracked pelagic seabirds: application of kernel estimation to albatross locations

We develop a new approach to quantifying habitat use within the foraging ranges of satellite-tracked seabirds. We applied kernel estimation techniques to 167 days (3738 locations) of data from Black-browed and Grey-headed albatrosses Diomedea melanophris and D. chrysostoma during the chick-rearing period of the breeding cycle at South Georgia. At this time the activity range of these two species covers an estimated 440 000 and 640 000 km², respectively, with very substantial overlap. In contrast, kernel estimation reveals that the main foraging areas of these two sympatric, congeneric species are very distinct. Based on location density categories accounting for 50% of locations, the foraging areas cover c. 81 500 and c. 119 700 km², respectively, with 42% and 50% of the range of one species overlapping with that of the other.     

Comparative tissue distribution of mercury,cadmium and zinc in three species of pelagic seabirds

1. The levels of mercury cadmium and zinc were measured in tissues of puffin (Fratercula arctica) fulmar (Fulmarus glacialis) and Manx shearwater (Puffinus puffinus).2. The highest levels of zinc and cadmium (up to 480mg/kg Cd, dry wt) were found in kidney, liver, pancreas, gonad, and intestine.3. Substantial quantities of mercury-mostly methyl mercury-were found in the liver of the fulmar nd Manx shearwater (up to 45.0 mg/kg Hg, dry wt).4. Puffin feathers contained more mercury (7.94 mg/kg Hg, dry wt) than the liver and kidney.5. The possibility that, since these birds were breeding they were not suffering any adverse effects of the metals, is discussed.     

Stable isotope evidence of diverse species-specific and individual wintering strategies in seabirds

Although there is increasing evidence that climatic variations during the non-breeding season shape population dynamics of seabirds, most aspects of their winter distribution and ecology remain essentially unknown. We used stable isotope signatures in feathers to infer and compare the moulting (wintering) habitat of subantarctic petrels breeding at two distant localities (South Georgia and Kerguelen). Petrels showed species-specific wintering habitat preferences, with a similar pattern of latitudinal segregation for all but one taxon. At both localities, delta13C values indicated that blue petrels (Halobaena caerulea) moult in Antarctic waters, South Georgian diving petrels (Pelecanoides georgicus) in the vicinity of the archipelagos and/or in the Polar Frontal Zone and Antarctic prions (Pachyptila desolata) in warmer waters. In contrast, common diving petrels (Pelecanoides urinatrix) showed divergent strategies, with low and high intrapopulation variation at South Georgia and Kerguelen, respectively. Birds from Kerguelen dispersed over a much wider range of habitats, from coastal to oceanic waters and from Antarctica to the subtropics, whereas those from South Georgia wintered mainly in waters around the archipelago. This study is the first to show such striking between-population heterogeneity in individual wintering strategies, which could have important implications for likely demographic responses to environmental perturbation.     

Climate oscillation and the invasion of alien species influence the oceanic distribution of seabirds

Spatial and temporal distribution of seabird transiting and foraging at sea is an important consideration for marine conservation planning. Using at‐sea observations of seabirds (n = 317), collected during the breeding season from 2012 to 2016, we built boosted regression tree (BRT) models to identify relationships between numerically dominant seabird species (red‐footed booby, brown noddy, white tern, and wedge‐tailed shearwater), geomorphology, oceanographic variability, and climate oscillation in the Chagos Archipelago. We documented positive relationships between red‐footed booby and wedge‐tailed shearwater abundance with the strength in the Indian Ocean Dipole, as represented by the Dipole Mode Index (6.7% and 23.7% contribution, respectively). The abundance of red‐footed boobies, brown noddies, and white terns declined abruptly with greater distance to island (17.6%, 34.1%, and 41.1% contribution, respectively). We further quantified the effects of proximity to rat‐free and rat‐invaded islands on seabird distribution at sea and identified breaking point distribution thresholds. We detected areas of increased abundance at sea and habitat use‐age under a scenario where rats are eradicated from invaded nearby islands and recolonized by seabirds. Following rat eradication, abundance at sea of red‐footed booby, brown noddy, and white terns increased by 14%, 17%, and 3%, respectively, with no important increase detected for shearwaters. Our results have implication for seabird conservation and island restoration. Climate oscillations may cause shifts in seabird distribution, possibly through changes in regional productivity and prey distribution. Invasive species eradications and subsequent island recolonization can lead to greater access for seabirds to areas at sea, due to increased foraging or transiting through, potentially leading to distribution gains and increased competition. Our approach predicting distribution after successful eradications enables anticipatory threat mitigation in these areas, minimizing competition between colonies and thereby maximizing the risk of success and the conservation impact of eradication programs.     

Trophic segregation of Falkland Islands seabirds: insights from stable isotope analysis

Seabird colonies provide rare opportunities to study trophic segregation in an entire bird community. We here present data on nitrogen and carbon isotope ratios of eight species of seabirds from New Island, Falkland Islands, and compare trophic levels (TL) and foraging distributions. We included adult feathers representing the interbreeding season, as well as chick feathers or down representing the breeding season. The stable isotope ratios indicated differences in feeding areas and TLs between species, consistent with the data of previous conventional diet analyses and observations at sea. We further reviewed conventional and stable isotope seabird community studies calculating the means and ranges of TLs observed across these studies. The mean TL (3.7) of the seabird community on New Island was at the lower end of the mean value range (3.5–4.5), but not significantly different, from the reviewed seabird communities. Seabirds on New Island had a range of 1.3 TLs, which is on the upper end of ranges within a community (0.4–1.5), indicating strong trophic structuring.     

Unexpected NRY chromosome variation in Northern Island Melanesia

To investigate the paternal population history of populations in Northern Island Melanesia, 685 paternally unrelated males from 36 populations in this region and New Guinea were analyzed at 14 regionally informative binary markers and 7 short tandem repeat (STR) loci from the nonrecombining portion of the Y chromosome. Three newly defined binary markers (K6-P79, K7-P117, and M2-P87) aided in identifying considerable heterozygosity that would have otherwise gone undetected. Judging from their geographic distributions and network analyses of their associated STR profiles, 4 lineages appear to have developed in this region and to be of considerable age: K6-P79, K7-P117, M2-P87, and M2a-P22. The origins of K5-M230 and M-M4 are also confirmed as being located further west, probably in New Guinea. In the 25 adequately sampled populations, the number of different haplogroups ranged from 2 in the single most isolated group (the Aita of Bougainville), to 9, and measures of molecular diversity were generally not particularly low. The resulting pattern contradicts earlier findings that suggested far lower male-mediated diversity and gene exchange rates in the region. However, these earlier studies had not included the newly defined haplogroups. We could only identify a very weak signal of recent male Southeast Asian genetic influence (<10%), which was almost entirely restricted to Austronesian (Oceanic)-speaking groups. This contradicts earlier assumptions on the ancestral composition of these groups and requires a revision of hypotheses concerning the settlement of the islands of the central Pacific, which commenced from this region.     

Spatial and temporal variation in mercury contamination of seabirds in the North Sea

Once the moult patterns have been taken into account, feather methylmercury levels can be used to accurately measure the mercury burdens of seabirds. We used body feathers from live seabirds and from museum collections to examine geographical and temporal patterns of mercury contamination in the North Sea. This approach identifies an increase in mercury concentrations in seabirds of the German North Sea coast during the last 100 years, especially high levels during the 1940s, and reduced contamination in the last few years. Comparisons among populations suggest that some increases in mercury levels are predominantly due to local pollution inputs, as on the German coast, while in other areas deposition from jet stream circulation of global contamination may be the major contributor. Mercury levels are far higher in seabirds from the German North Sea coast than in populations from the north and west North Sea or from most areas of the North Atlantic. We advocate the use of museum collections of birds for studies of long-term changes in levels of mercury contamination.     

Intraspecific variation in the pelagic larval duration of tropical reef fishes

Estimates of pelagic larval duration (PLD) for 10 species of Pomacentridae and two species of Gobiidae were made. In eight of the 12 species examined, within‐population mean PLDs differed between sampling times, locations within regions and among regions. In contrast, the range of these same PLD estimates overlapped at all spatial and temporal scales examined in 11 of the 12 species, but not between regions in one species ( Amphiprion melanopus ). Therefore, despite tight error estimates typically associated with estimates of PLD taken from a particular population at a particular time in some taxa, the overlapping ranges in PLD reported here indicate that the length of the pelagic larval phase is a much more plastic trait than previously appreciated. Within‐species variation in PLD has considerable potential to provide further insights into the ecology and evolution of tropical reef fishes.     

Individual migratory patterns of two threatened seabirds revealed using stable isotope and geolocation analyses

Aim

Intraspecific variability in the migratory movements of seabirds is being revealed far more complex than hitherto recognized, and our lack of understanding undermines their effective protection. Our aim is to test whether the isotopic values of a single feather of two threatened seabirds, the Mediterranean (Puffinus yelkouan) and the Balearic (Puffinus mauretanicus) shearwaters allow the geographic assignment of birds to their non‐breeding areas.

Location

These two species are known to use three main non‐breeding areas: the NE Atlantic Ocean, the W Mediterranean and the Aegean‐Black seas.

Methods

We clustered in three groups the δ¹³C and δ¹⁵N values of the first primary feather (P1), inferred to be grown during the non‐breeding period, of 34 Mediterranean and 56 Balearic shearwaters accidentally caught by longliners. To link the isotopic values of P1 to its corresponding non‐breeding area, we performed a discriminant function analysis (DFA) based on the three clusters and applied this function to feathers of known origin: P1 from seven Mediterranean shearwaters from Hyères Archipelago (France) tracked with geolocators and body feathers from six chicks from Balearic shearwaters. To link the moulting patterns to the areas where the feathers were grown, we applied the DFA to a sequence of primary feathers of eight Balearic and five Mediterranean shearwaters (caught by longliners).

Results

Isotopic and tracking data indicate that none of the Mediterranean shearwaters migrated to the Atlantic. The cluster and discriminant function analyses revealed that 8% of Balearic and 54% of Mediterranean shearwater moulted P1 in the Mediterranean Sea. Migratory movements were reflected in the changing isotopic values of the primary sequences.

Main conclusions

Stable isotope analyses (SIA) are a powerful approach to reveal the intraspecific variability in the migratory patterns of seabirds that use distinct isotopic areas over their annual cycle. The assignment of birds to their non‐breeding areas by means of SIA is a simple and effective tool that can help to evaluate the impact of human activities in remote areas not only at population but also at individual level, which is an essential knowledge for the management and conservation of threatened species.