Shifting access to pools of shoot water sustains gas exchange and increases stem hydraulic safety during seasonal atmospheric drought

Understanding how plants acclimate to drought is crucial for predicting future vulnerability, yet seasonal acclimation of traits that improve drought tolerance in trees remains poorly resolved. We hypothesized that dry season acclimation of leaf and stem traits influencing shoot water storage and hydraulic capacitance would mitigate the drought-associated risks of reduced gas exchange and hydraulic failure in the mangrove Sonneratia alba. By late dry season, availability of stored water had shifted within leaves and between leaves and stems. While whole shoot capacitance remained stable, the symplastic fraction of leaf water increased 86%, leaf capacitance increased 104% and stem capacitance declined 80%. Despite declining plant water potentials, leaf and whole plant hydraulic conductance remained unchanged, and midday assimilation rates increased. Further, the available leaf water between the minimum water potential observed and that corresponding to 50% loss of stem conductance increased 111%. Shifting availability of pools of water, within and between organs, maintained leaf water available to buffer periods of increased photosynthesis and losses in stem hydraulic conductivity, mitigating risks of carbon depletion and hydraulic failure during atmospheric drought. Seasonal changes in access to tissue and organ water may have an important role in drought acclimation and avoidance.

Foliar water uptake via cork warts in mangroves of the Sonneratia genus

Foliar water uptake (FWU) occurs in plants of diverse ecosystems; however, the diversity of pathways and their associated FWU kinetics remain poorly resolved. We characterized a novel FWU pathway in two mangrove species of the Sonneratia genus, S. alba and S. caseolaris. Further, we assessed the influence of leaf wetting duration, wet-dry seasonality and leaf dehydration on leaf conductance to surface water (K_surf ). The symplastic tracer dye, disodium fluorescein, revealed living cells subtending and encircling leaf epidermal structures known as cork warts as a pathway of FWU entry into the leaf. Rehydration kinetics experiments revealed a novel mode of FWU, with slow and steady rates of water uptake persistent over a duration of 12 hr. K_surf increased with longer durations of leaf wetting and was greater in leaves with more negative water potentials at the initiation of leaf wetting. K_surf declined by 68% between wet and dry seasons. Our results suggest that FWU via cork warts in Sonneratia sp. may be rate limited and under active regulation. We conclude that FWU pathways in halophytes may require ion exclusion to avoid uptake of salt when inundated, paralleling the capacity of halophyte roots for ion selectivity during water acquisition.

Seabird bycatch in pelagic longline fisheries is grossly underestimated when using only haul data

Hundreds of thousands of seabirds are killed each year as bycatch in longline fisheries. Seabirds are predominantly caught during line setting but bycatch is generally recorded during line hauling, many hours after birds are caught. Bird loss during this interval may lead to inaccurate bycatch information. In this 15 year study, seabird bycatch was recorded during both line setting and line hauling from four fishing regions: Indian Ocean, Southern Ocean, Coral Sea and central Pacific Ocean. Over 43,000 albatrosses, petrels and skuas representing over 25 species were counted during line setting of which almost 6,000 seabirds attempted to take the bait. Bait-taking interactions were placed into one of four categories. (i) The majority (57%) of bait-taking attempts were “unsuccessful” involving seabirds that did not take the bait nor get caught or hooked. (ii) One-third of attempts were “successful” with seabirds removing the bait while not getting caught. (iii) One-hundred and seventy-six seabirds (3% of attempts) were observed being “caught” during line setting, with three albatross species – Laysan (Phoebastria immutabilis), black-footed (P. nigripes) and black-browed (Thalassarche melanophrys)– dominating this category. However, of these, only 85 (48%) seabird carcasses were retrieved during line hauling. Most caught seabirds were hooked through the bill. (iv) The remainder of seabird-bait interactions (7%) was not clearly observed, but likely involved more “caught” seabirds. Bait taking attempts and percentage outcome (e.g. successful, caught) varied between seabird species and was not always related to species abundance around fishing vessels. Using only haul data to calculate seabird bycatch grossly underestimates actual bycatch levels, with the level of seabird bycatch from pelagic longline fishing possibly double what was previously thought.

The feeding ecology and field energetics of the Pedra Branca skink (Niveoscincus palfreymani)

The diet and food requirements of free-living Pedra Branca skinks (Niveoscincus palfreymani) were studied on Pedra Branca Island, the only known location for this vulnerable, endemic species. While discarded fish remains and regurgitate from seabirds are utilised as food by the skinks during summer, invertebrates represent the most important prey. Isotope turnover rates indicate that feeding is negligible over winter and that significant amounts of non-food water are turned over during summer, either by drinking rainwater or as pulmo-cutaneous water exchange. An assessment is made of the seasonal and annual food requirements of individual skinks and the population.

Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). I. Estimates of mortality

The bulk ore carrier Iron Baron ran aground on Hebe Reef at the mouth of the Tamar River in northern Tasmania, Australia, on 10 July 1995. It released an estimated 325 tonnes of bunker fuel oil. Of the wildlife species affected, the most readily detected was the little penguin (Eudyptula minor); 1894 were collected and treated for oiling. This study estimates the impact of the oil spill on populations of little penguins. At Ninth Island (approximately 40 km from Hebe Reef), one of the most affected little penguin colonies, pre-oil-spill population estimates were available. Extensive regular trapping and mark–recapture of birds at this site during the course of the oil spill provided longitudinal data on oiling rates from a known population size. Using these data, we estimate that 19.6% of birds from Ninth Island were oiled and survived to come ashore. This represents about 526 (1932–3108, 95% CL) adult birds, or up to 5566 (4197–6917) birds in total (adults and juveniles). For estimates of the impact on little penguin populations in the region, we provide three scenarios of the possible numbers of penguins oiled. After considering the biases of each risk assessment, we believe that between 10 000 and 20 000 penguins were killed as a result of the oil spill. The study indicates that, despite the relatively small amount of oil spilt by the Iron Baron, the impact on penguin populations was extensive. This study also highlights the difficulties and requirements in assessing the impact of oil spills on wildlife populations.

Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). II. Post-release survival of rehabilitated oiled birds

The post-release survival of rehabilitated oiled little penguins (Eudyptula minor) was monitored over 20 months following the Iron Baron oil spill (10 July 1995) in northern Tasmania, Australia. During rehabilitation, over 1800 little penguins were individually banded and detailed records kept of factors including their degree of oiling, sex, capture and release mass and capture and release condition. Post-release survival of rehabilitated oiled little penguins was assessed through regular trapping of birds over two breeding sites (Ninth Island and Low Head). The minimum estimate of post-release survival was 59% for penguins from Ninth Island and 44% for penguins from Low Head. Rehabilitated oiled little penguins had significantly lower survival than non-oiled birds at both sites. The main factor affecting post-release survival was the extent of oiling, which itself had a significant influence on the capture mass and condition of birds. Combined, these factors had the greatest power to predict post-release survival. Other factors that significantly affected post-release survival included release mass and condition, and the sex of the bird. The duration of rehabilitation and whether birds were translocated (200–410 km) from their capture site prior to release did not significantly affect survival. The results of this study indicate how aspects of oiling, the condition of birds and rehabilitation affect post-release survival. As such, they will help improve the success of wildlife rehabilitation in future spills, and highlight the importance of individually marking rehabilitated oiled wildlife and post-release monitoring in assessing the success of rehabilitation programs.

Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). III. Breeding success of rehabilitated oiled birds

The long-term effects of oiling on the breeding success of rehabilitated oiled little penguins (Eudyptula minor) were examined over two consecutive breeding seasons following the Iron Baron oil spill in 1995. The commencement of egg laying was delayed among rehabilitated oiled penguins compared with non-oiled birds during the 1995/96 breeding season. During that season, hatching success (number of eggs hatched from those laid) was no different in nests containing rehabilitated oiled penguins than in those containing non-oiled birds, but overall egg success (number of pre-fledging chicks from the number of eggs laid) was significantly lower among rehabilitated oiled birds. This effect was predominant in nests containing a rehabilitated oiled female, where the probability of successfully fledging any chicks was 22% lower than in nests containing a non-oiled female. During the 1996/97 breeding season, there was no significant difference between either the hatching or egg success of rehabilitated oiled penguins and non-oiled birds. In both seasons, the pre-fledging masses of chicks from rehabilitated oiled penguins were significantly lower than those from non-oiled birds. The chicks of rehabilitated oiled penguins were therefore expected to have lower survival than chicks raised by non-oiled parents. Results indicate that oiling not only reduced the number of chicks raised by rehabilitated oiled penguins in the short term, but also decreased the quality of young produced for at least two seasons following the spill.

Reliability of morphometric measures for determining the sex of adult and fledgling shy albatrosses, Diomedea cauta cauta, in Australia

Dissection and measurement of the carcasses of shy albatrosses, Diomedea cauta cauta, provided morphometric data from known-sex birds from fledgling age to adulthood. These data were used to determine the efficacy of external measures for reliably identifying the sex of birds in the field. As fledglings were smaller than adults and subadults in all measures, separate age-specific equations were developed for assigning their sex. Sexual dimorphism was evident in all head, beak and leg measurements for the adult and subadult birds, with males being significantly larger than females, while there were no sex differences in measures of the wings and tail. Beak and head measurements, along with the weight of fledglings, were taken, and sex differences were evident for all parameters. A stepwise discriminant function analysis of the seven head and beak measures (head length, head width, basal bill width, culmen length, basal bill depth, minimum bill depth and upper bill depth) indicated that 98% of adult and subadult birds could be correctly sexed by measuring the upper bill depth and head width, whilst the sex of 89% of fledglings could be discerned by measuring head length and width and the minimum bill depth. Discriminant scores overlapped less for adults–subadults than for fledglings, indicating that external measurements may be used more reliably to sex this age-class. Data from three experienced observers indicated significant differences in the morphometric measures taken from the same individual albatrosses. The extent of these differences, however, varied greatly depending on the measure taken (i.e. beak v. wing measures), with head and beak measures showing the least inter-observer differences. Such differences resulted in a decrease in the success rate of the adult–subadult discriminant function analysis from 98 to 90%. When working with breeding birds, sex-allocation errors can be reduced by measuring both members of a pair and allowing the relative size of the discriminant score to identify the individuals concerned.

Prey harvest of the Australasian gannet (Sula serrator) in Tasmania

This study investigated the diet of the Australasian gannet (Sula serrator) at Pedra Branca, an island off the south coast of Tasmania. A total of 109 regurgitations representing 394 prey items was collected from the gannets between 1986 and 1991. Pelagic schooling fish, with fork length less than 200 mm, were the most common prey items. Redbait (Emmelichthys nitidus) and jack mackerel (Trachurus declivis) were the dominant prey species, with redbait being the most numerous, contributing 72% by number and 56% by mass. The diet of the Australasian gannet was compared with the fish taken by the commercial purse seine fishery in which jack mackerel was the target species and redbait a bycatch. The mean size of commercially caught fish of both species was greater than that taken by the gannets. We suggest that there is a threshold (in the size of the fish) above which the birds cannot capture and handle the prey, effectively limiting the resource available to them. It appears that the commercial fishery and the gannets, while harvesting the same species, exploit schools of different-size fish. The potential of Australasian gannets as indicators of fish stocks is discussed.

DDT and dieldrin: effects on resident Peregrine Falcon populations in south-eastern Australia

Organochlorine residues in eggs and prey species of the Peregrine Falcon,Falco peregrinus, were determined in parts of three south-eastern Australian States: Tasmania (1975-91), Victoria (1975-83) and South Australia (1977-1981). Relationships between residues detected and eggshell thickness, nest site occupancy and productivity were examined. Temporal changes and, in particular, the relative effects of DDE and dieldrin were also investigated. DDE was detected in all 137 eggs analysed. The concentration of DDE residues in eggs peaked in the late 1970s to early 1980s in Victoria, but peaked earlier and had declined to low concentrations by the 1980s in Tasmania. Maximum concentrations reached 82 ppm, in Victoria. The geometric means were: Victoria 12.4 ppm; Tasmania 1970s 10.1 ppm, 1980s 1.5 ppm; and South Australia 1.95 ppm. Dieldrin was detected in approximately half the eggs, but all except one egg (1.5 ppm) contained concentrations considered noncritical (<1 ppm). The degree of shell-thinning and reproductive success were related to DDE content, but not to that of dieldrin.Organochlorine concentrations in prey reflected general concentrations in eggs and, with a few exceptions, were low. In Tasmania, reproductive success increased as DDE contamination declined. In Victoria, despite mean concentrations of DDE well above that considered to be critical for successful reproduction (>15-20 ppm) for at least seven years, the breeding population declined by <2% a year. We interpret this result as evidence that DDE causes a slow decline in population and that the dramatic declines observed in some other parts of the world were mainly attributable to contamination by dieldrin or to other confounding factors.

Status of Australian and New-Zealand Fur Seals at Maatsuyker Island, Southwestern Tasmania

Surveys were carried out between 1987 and 1989 on Maatsuyker I. and nearby Needle Rocks off southern Tasmania to establish the status and identification of the seals present. New Zealand fur seals, Arctocephalus forsteri, were found on Maatsuyker I. There were at least 15 pups born on the island in 1987/88. Australian fur seals, Arctocephalus pusillus doriferus, use the islands as a haulout site but do not breed here. The distribution of New Zealand fur seals can now be amended to include Tasmanian waters. Records discussed here also alter aspects of the status of Australian fur seals because the Maatsuyker group is not a breeding site for this species and breeding colonies are therefore restricted to Bass Strait waters.

Water, Sodium and Energy Turnover in Free-Living Little Penguins, Eudyptula-Minor

Water influx rates of adult little penguins ranged from 20 ml kg-' day-' in fasting (incubating and moulting) birds to about 650 ml kg-' day- ' in birds that were foraging at sea over extended periods. The sodium influx rates of adults ranged from almost zero up to 87 mmol kg-' day-', depending on the activity patterns of the birds, and were closely correlated with water influxes. The metabolic rates of adult penguins were 1.7 and 2.8 times standard metabolic rates during fasting and foraging respectively, and were also closely correlated with water influx rates. The mean food consumption rate for the maintenance of chicks was about 236 g kg-' day-', equivalent to a maintenance energy intake of 1460 kJ kg-' day-'. Partitioning calculations show that sea water ingestion during foraging represented about 10% of total water influx, but about 40% of total sodium influx. Nasal salt secretions were hyperosmotic to serum and it was calculated that daily sodium influxes could be totally eliminated via this route within 4 hours.

The isolation of arboviruses including a new flavivirus and a new Bunyavirus from Ixodes (Ceratixodes) uriae (Ixodoidea: Ixodidae) collected at Macquarie Island, Australia, 1975-1979

Pools of ticks, Ixodes (Ceratixodes) uriae collected between 1975 and 1979 at Macquarie Island, yielded 33 strains of at least 4 different viruses: Nugget virus (Kemerovo group), 1 strain; Taggert virus (Sakhalin group) 9 strains; a previously undescribed flavivirus, related to Central European Tickborne encephalitis virus, for which the name "Gadgets Gully" is proposed, 9 strains; a virus serologically related to the Uukuniemi serogroup, family Bunyaviridae, for which the name "Precarious Point" is proposed, 10 strains. Three isolates were mixtures of Nugget and Gadgets Gully viruses; the remaining virus strain remains unidentified.