INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE1

Streamside vegetation frequently regenerates faster than upland vegetation following wildland fire and contributes to the recovery of riparian and stream ecosystems. Limited data are available, however, on the post‐fire growth of riparian species and the influence of herbivory on regeneration. To determine post‐fire regrowth of riparian vegetation, height, crown area, crown volume, and browse levels were measured for key riparian shrub species in streamside burned and unburned plots along second‐order streams in western Wyoming. Shrubs in the burned plots were subject to high levels of browse ‐ up to 84 percent of the leaders were browsed ‐ by native ungulates in 2002, the second post‐fire year (September 2001 to September 2002). In summer 2003, the burned watershed was also grazed by livestock, resulting in increased browse levels and decreased shrub heights for several species. In the third post‐fire year, September 2002 to September 2003, four of the six most common species showed no increase in crown area or crown volume, indicating that the combination of native ungulate and cattle browsing suppressed their growth. Potential impacts of grazing on post‐fire recovery of stream and riparian ecosystems are discussed.     

Long-term behavior at foraging sites of adult female loggerhead sea turtles (Caretta caretta) from three Florida rookeries

We used satellite telemetry to study behavior at foraging sites of 40 adult female loggerhead sea turtles (Caretta caretta) from three Florida (USA) rookeries. Foraging sites were located in four countries (USA, Mexico, the Bahamas, and Cuba). We were able to determine home range for 32 of the loggerheads. One turtle moved through several temporary residence areas, but the rest had a primary residence area in which they spent all or most of their time (usually >11 months per year). Twenty-four had a primary residence area that was <500 km² (mean = 191). Seven had a primary residence area that was ≥500 km² (range = 573–1,907). Primary residence areas were mostly restricted to depths <100 m. Loggerheads appeared to favor areas with larger-grained sediment (gravel and rock) over areas with smaller-grained sediment (mud). Short-term departures from primary residence areas were either looping excursions, typically involving 1–2 weeks of continuous travel, or movement to a secondary residence area where turtles spent 25–45 days before returning to their primary residence area. Ten turtles had a secondary residence area, and six used it as an overwintering site. For those six turtles, the primary residence area was in shallow water (<17 m) in the northern half of the Gulf of Mexico (GOM), and overwintering sites were farther offshore or farther south. We documented long winter dive times (>4 h) for the first time in the GOM. Characterizing behaviors at foraging sites helps inform and assess loggerhead recovery efforts.     

Exploring the potential of otolith microchemistry to enhance diet analysis in pinnipeds

Increasing the scope and accuracy of information about pinniped diets obtainable from non-invasive techniques is increasingly important, particularly in cases where pinniped species are threatened or endangered. This study is the first to explore the potential for using elemental analysis of the otoliths found in scat to enhance the information available for diet analyses. We investigated the effects of pinniped digestion on otolith microchemistry using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). We compared the elements contained in the edges (adult stage) and cores (larval/juvenile stage) of otoliths from Pacific herring (Clupea pallasii), Atka mackerel (Pleurogrammus monopterygius), and Walleye pollock (Theragra chalcogramma) recovered from the scat of captive Steller sea lions (Eumetopias jubatus) to elements in a sample of pristine (undigested) otoliths. We found that digestion had a significant effect on four of the six sampled combinations of species and otolith region (herring edges and cores, mackerel edges, and pollock cores), and that Rb most frequently showed significant differences in concentration after digestion. We could significantly discriminate among species of both pristine and digested otoliths using either otolith edges or cores with the elements Ba, Rb, Sr, Y, and Mg. When compared to previously identified digested otoliths, unknown samples of the three species of digested otoliths could be discriminated with 55–100% accuracy depending on species and otolith region. When compared to a library of previously identified pristine and digested otoliths, unknown samples of digested otoliths could be discriminated to species with 65–88% accuracy. When the group of unknown digested otoliths was compared to known pristine otoliths, discrimination ranged from 45 to 65%. These results indicate that elemental analysis could be used to supplement visual identification of otoliths from scat. However, further research is required to determine whether elemental analysis of digested otoliths could be useful for prey fish population studies.     

Use of environmental DNA in assessment of fish functional and phylogenetic diversity

Assessing the impact of global changes and protection effectiveness is a key step in monitoring marine fishes. Most traditional census methods are demanding or destructive. Nondisturbing and nonlethal approaches based on video and environmental DNA are alternatives to underwater visual census or fishing. However, their ability to detect multiple biodiversity factors beyond traditional taxonomic diversity is still unknown. For bony fishes and elasmobranchs, we compared the performance of eDNA metabarcoding and long-term remote video to assess species’ phylogenetic and functional diversity. We used 10 eDNA samples from 30 L of water each and 25 hr of underwater videos over 4 days on Malpelo Island (pacific coast of Colombia), a remote marine protected area. Metabarcoding of eDNA detected 66% more molecular operational taxonomic units (MOTUs) than species on video. We found 66 and 43 functional entities with a single eDNA marker and videos, respectively, and higher functional richness for eDNA than videos. Despite gaps in genetic reference databases, eDNA also detected a higher fish phylogenetic diversity than videos; accumulation curves showed how 1 eDNA transect detected as much phylogenetic diversity as 25 hr of video. Environmental DNA metabarcoding can be used to affordably, efficiently, and accurately census biodiversity factors in marine systems. Although taxonomic assignments are still limited by species coverage in genetic reference databases, use of MOTUs highlights the potential of eDNA metabarcoding once reference databases have expanded.     

Degradation of Polyethylene Designed for Agricultural Purposes

For many years now, scientific articles have been published on the potential biodegradability of polyethylene. Polyethylene (PE) with peroxidant additives, in the form of agricultural films, is sold by various suppliers as biodegradable mulch. Even though, the photo-chemical and thermal degradation of these products under artificial laboratory conditions is highlighted, several extrapolation on the biodegradation and, moreover, on the neutral environmental impact of PE are made. In this study, three different commercial mulch films have been submitted to standardised biodegradation tests and the results are discussed. The first conclusions are that a very low degree of biodegradation of the commercial PE films is achieved from these tests and that crosslinked PE micro-fragments are found in soil after a very long period of time.     

First fossil evidence of an “interglacial refugium” in the Pyrenean region

A refugium is generally understood as an area where temperate species survive cold periods, such as the Iberian, Italian, or Balkan Peninsulas in Europe. Strictly speaking, this definition refers to what is known as a glacial refugium. However, there are various types of lesser-known refugia such as the interglacial refugium, which denotes a mountainous region at low latitudes, such as the Pyrenees, where species adapted to the cold survive during interstadial periods. The small-vertebrate association from the sequence of Cova Colomera, which is located on the southern face of the Pyrenees and contains the final cold spell of the Late Pleistocene and the beginnings of the temperate period in which we currently find ourselves (the Holocene), could constitute the first fossil evidence of such an interglacial refugium, thus providing new paleoecological data on the phenomenon.     

Modelling the dynamic air-water-sediment coupled fluxes and occurrence of polychlorinated biphenyls in a high altitude lake

The BIODEP model in terms of atmosphere-lake interactions was developed. The model was applied to an oligotrophic, dimictic high altitude lake (Lake Redo, Pyrenees) for a range of polychlorinated biphenyl (PCB) congeners. High altitude lakes, which receive their contaminant inputs uniquely from the atmosphere through long-range atmospheric transport, provide ideal controlled environments for the study of the interactions between atmospheric depositional and water column biogeochemical processes. The BIODEP model was able to predict dissolved water concentrations and PCB accumulation in the lake sediment within a factor of 2. This shows that the BIODEP model captures the essential processes driving the sink of POPs in high altitude lakes and that POP occurrence in the lake is driven by direct atmospheric inputs with limited influence from the watershed. An important seasonal variability in water column concentrations is predicted which should have important implications in sampling strategies. Furthermore, it is shown that diffusive air-water exchange dominated the PCB dynamics in the lake, especially for the less chlorinated biphenyls.