Variation in age of primiparity in mountain goats estimated from horn growth increments

Variation in age of primiparity is important for population dynamics and wildlife management because it can affect population growth. Using a novel technique based on the trade-off between annual horn growth and reproduction, we estimated the age of primiparity for 2274 female mountain goats (Oreamnos americanus, de Blainville 1816) harvested across British Columbia, Canada, from 1976 to 2019. We then investigated spatio-temporal variation in the probability that harvested females were primiparous when aged three, four or five years and older using Bayesian ordinal regressions. We found that the probability of primiparity at three years decreased over time in nearly all mountain ranges. In the Coastal Mountain range, however, the probability of primiparity at age three significantly increased. These results suggest that the large coastal populations of mountain goats could be more resilient to harvest than other populations in British Columbia, which may be experiencing environmental effects promoting later primiparity. Models predicting age of primiparity from annual growth measures are a valuable tool for wildlife management and could help conservation of many species.

Growth and feeding ecology of coniform conodonts

Conodonts were the first vertebrates to develop mineralized dental tools, known as elements. Recent research suggests that conodonts were macrophagous predators and/or scavengers but we do not know how this feeding habit emerged in the earliest coniform conodonts, since most studies focus on the derived, ‘complex’ conodonts. Previous modelling of element position and mechanical properties indicate they were capable of food processing. A direct test would be provided through evidence of in vivo element crown tissue damage or through in vivo incorporated chemical proxies for a shift in their trophic position during ontogeny. Here we focus on coniform elements from two conodont taxa, the phylogenetically primitive Proconodontus muelleri Miller, 1969 from the late Cambrian and the more derived Panderodus equicostatus Rhodes, 1954 from the Silurian. Proposing that this extremely small sample is, however, representative for these taxa, we aim to describe in detail the growth of an element from each of these taxa in order to the test the following hypotheses: (1) Panderodus and Proconodontus processed hard food, which led to damage of their elements consistent with prey capture function; and (2) both genera shifted towards higher trophic levels during ontogeny. We employed backscatter electron (BSE) imaging, energy-dispersive X-ray spectroscopy (EDX) and synchrotron radiation X-ray tomographic microscopy (SRXTM) to identify growth increments, wear and damage surfaces, and the Sr/Ca ratio in bioapatite as a proxy for the trophic position. Using these data, we can identify whether they exhibit determinate or indeterminate growth and whether both species followed linear or allometric growth dynamics. Growth increments (27 in Pa. equicostatus and 58 in Pr. muelleri) were formed in bundles of 4–7 increments in Pa. equicostatus and 7–9 in Pr. muelleri. We interpret the bundles as analogous to Retzius periodicity in vertebrate teeth. Based on applied optimal resource allocation models, internal periodicity might explain indeterminate growth in both species. They also allow us to interpret the almost linear growth of both individuals as an indicator that there was no size-dependent increase in mortality in the ecosystems where they lived e.g., as would be the case in the presence of larger predators. Our findings show that periodic growth was present in early conodonts and preceded tissue repair in response to wear and damage. We found no microwear and the Sr/Ca ratio, and therefore the trophic position, did not change substantially during the lifetimes of either individual. Trophic ecology of coniform conodonts differed from the predatory and/or scavenger lifestyle documented for “complex” conodonts. We propose that conodonts adapted their life histories to top-down controlled ecosystems during the Nekton Revolution.

Native Forests Show Resilience to Selective Timber Harvesting in Southeast Queensland, Australia

There is little published information on effects of management on the structure of mixed species forests in Queensland, Australia. We used long-term growth, abundance and dimension data from permanent plots to test the hypothesis that harvesting would reduce numbers of large trees and growth increments, while increasing recruitment. This hypothesis is key to policy and management decisions for forests covering about 9.5 million hectares. Inclusion of data on changes in forest structure (e.g., tree diameter, stem density) helps in assessment of forest suitability as habitat for a range of species. Growth rate (basal area) varied widely among forest types. Growth of each of four key species (i.e., Eucalyptus pilularis, Corymbia citriodora ssp. variegata, Callitris glaucophylla, and Eucalyptus crebra) reflected variation in rainfall across the study region. Callitris glaucophylla, a native conifer, is dominant when rainfall is < 600 mm per year. Corymbia citriodora ssp. variegata grows across much wider ranges in rainfall (600–1,200 mm year–1) at rates similar to Callitris glaucophylla. Historic harvesting increased recruitment and also increased the symmetry of diameter distributions. Harvesting has not reduced the current density of larger trees (diameter at breast height, DBH ≥ 60 cm) at a regional scale. Stand growth was unaffected by management principally owing to an increase in the density of trees of smaller diameter (10–20 cm DBH). Self-thinning limits potential stocking and we tested 3 methods for predicting self-thinning across forest types. We found that the slope of self-thinning lines under drier conditions is mostly < –2, suggesting highly dynamic self-thinning. Using a species-boundary line approach, growth is predicted to slow when basal areas reach around 66.1 m2 ha–1 in E. pilularis, 19.0 m2 ha–1 in C. citriodora ssp. variegata, 16.5 m2 ha–1 in Callitris glaucophylla, and 14.2 m2 ha–1 in E. crebra. The slope of the self-thinning line for E. pilularis was –1.662, similar to Reineke’s Stand Density Index (slope –1.605). To date, there is little evidence that selective harvesting and thinning have had negative impacts on rates of growth, on timber production, carbon sequestration or on aspects of forest structure regarded as important for biodiversity.

EVIDENCE OF MASS MORTALITY OF THE LONG-LIVED BIVALVE MERCENARIA STIMPSONI CAUSED BY A CATASTROPHIC TSUNAMI

ABSTRACT Tsunamis are huge disasters that can significantly damage benthic organisms and the sea-bottom environment in coastal areas. It is of great ecological importance to understand how benthic ecosystems respond to such destructive forces and how individual species are affected. Investigating the effect of such disasters on animals that are seldom caught alive is particularly difficult. Bivalve mollusks are especially suitable for investigating how a tsunami affects coastal benthic species because they preserve an environmental record in their shells that can be extended back in time by crossdating the records of multiple individuals. Here we studied dead shells of Mercenaria stimpsoni, a long-lived clam, and precisely determined the time of death by using nuclear bomb–induced radiocarbon (bomb-14C) and by counting annual growth increments. First, a quasi-continuous, regional bomb-14C record was created by analyzing the shells of 6 live-caught M. stimpsoni individuals. Then 27 dead shells collected from the seafloor of Funakoshi Bay were 14C-dated and analyzed. The results showed that the huge tsunami that struck northeastern Japan on 11 March 2011 caused mass mortality of this bivalve in Funakoshi Bay. Nine of the 27 clams died during the March 2011 tsunami, probably by starvation after burial by tsunami deposits or exposure above the seafloor as a result of sediment liquefaction during the earthquake. The dating method used in this study can help us understand how long-lived marine organisms with low population density are affected by huge natural disasters such as a tsunami.

Reconstruction of historic fossil CO₂ emissions using radiocarbon measurements from tree rings

<p>This project aims to reconstruct historic fossil fuel derived CO₂ (CO₂ff) emissions from two closely located point sources in Taranaki, New Zealand. The Vector gas processing plant and the Ballance agri-nutrients ammonia urea plant have combined emissions of ~0.16 TgC yr⁻¹ since 1970 and 1982 respectively. Previous work found 2–5 ppm CO₂ff in short term integrated samples collected 600m downwind of the Vector plant. This study extends the dataset back 30 years using radiocarbon measurements in tree rings. Trees incorporate CO₂ from the local atmosphere into their annual growth rings. Measurements of ¹⁴C in polluted and clean air trees were compared to the Baring Head Δ¹⁴CO₂ atmospheric record. As CO₂ff emissions are devoid of ¹⁴C addition of CO₂ff will cause a decrease in ¹⁴C directly related to the amount of CO₂ff present. Trees growing immediately downwind of the Vector plant and from clean air locations in Taranaki and Baring Head Wellington, were cored and cut into one year growth increments. Two cellulose preparation methods were tested to confirm effectiveness at removing mobile extractive components and lignin. Radiocarbon and stable isotope results showed that the ANSTO method was more effective than the Rafter method. The clean air trees compare well with the Baring Head atmospheric record whereas trees growing downwind of the Vector plant demonstrate lower ¹⁴C content consistent with CO₂ff addition. Historic CO₂ff emissions were reconstructed for the polluted trees, with 1–3ppm of CO₂ff in the Luscombe chestnut tree and 4–7 ppm CO₂ff in the Vector pine tree. CO₂ff observations were compared with reported emissions from the Vector and Ballance plants. Observed CO₂ff increased by 10% in the Vector pine tree for the period 1994–2012 relative to pre-1994 levels, whereas combined CO₂ff emissions increased by 64%. No increase was observed in the Luscombe chestnut tree for the same time period. Meteorological analysis was performed to assess the relative contribution of CO₂ff from the sources to the trees. It is proposed that the trend observed in the Vector pine is due to the dominance of emissions from the Ballance plant and a relatively minor contribution from the Vector plant.</p>

Reconstruction of historic fossil CO₂ emissions using radiocarbon measurements from tree rings

<p>This project aims to reconstruct historic fossil fuel derived CO₂ (CO₂ff) emissions from two closely located point sources in Taranaki, New Zealand. The Vector gas processing plant and the Ballance agri-nutrients ammonia urea plant have combined emissions of ~0.16 TgC yr⁻¹ since 1970 and 1982 respectively. Previous work found 2–5 ppm CO₂ff in short term integrated samples collected 600m downwind of the Vector plant. This study extends the dataset back 30 years using radiocarbon measurements in tree rings. Trees incorporate CO₂ from the local atmosphere into their annual growth rings. Measurements of ¹⁴C in polluted and clean air trees were compared to the Baring Head Δ¹⁴CO₂ atmospheric record. As CO₂ff emissions are devoid of ¹⁴C addition of CO₂ff will cause a decrease in ¹⁴C directly related to the amount of CO₂ff present. Trees growing immediately downwind of the Vector plant and from clean air locations in Taranaki and Baring Head Wellington, were cored and cut into one year growth increments. Two cellulose preparation methods were tested to confirm effectiveness at removing mobile extractive components and lignin. Radiocarbon and stable isotope results showed that the ANSTO method was more effective than the Rafter method. The clean air trees compare well with the Baring Head atmospheric record whereas trees growing downwind of the Vector plant demonstrate lower ¹⁴C content consistent with CO₂ff addition. Historic CO₂ff emissions were reconstructed for the polluted trees, with 1–3ppm of CO₂ff in the Luscombe chestnut tree and 4–7 ppm CO₂ff in the Vector pine tree. CO₂ff observations were compared with reported emissions from the Vector and Ballance plants. Observed CO₂ff increased by 10% in the Vector pine tree for the period 1994–2012 relative to pre-1994 levels, whereas combined CO₂ff emissions increased by 64%. No increase was observed in the Luscombe chestnut tree for the same time period. Meteorological analysis was performed to assess the relative contribution of CO₂ff from the sources to the trees. It is proposed that the trend observed in the Vector pine is due to the dominance of emissions from the Ballance plant and a relatively minor contribution from the Vector plant.</p>

Effect of Temperature on the Daily Increment Deposition in the Otoliths of European Sardine Sardina pilchardus (Walbaum, 1792) Larvae

Otolith microstructure analysis is a valuable tool to evaluate the relationship between larval age and growth and how it relates to environmental variability. Otolith growth and daily increment deposition were analyzed in sardine (Sardina pilchardus) larvae reared in the laboratory under different temperatures (13, 15, and 17 °C), with a diet rich in microalgae, rotifers, and copepods Acartia grani. The number and width of growth increments, first-check and otolith diameter were determined in the otoliths and then related to larval age and total length. At hatching, the sagittal otoliths consisted of a lenticular core with a diameter of 10.56 μm (±1.07 μm SD). Somatic growth increased with the increasing temperature and the growth rate of larvae reared at 13 and 15 °C was significantly lower than for larvae reared at 17 °C. At 17 °C, otoliths exhibited a higher diameter with wider increments than at 13 °C. There was a high variability of increment counts-at-age for larvae reared within the same temperature treatment. The increase of growth increments with larval size was higher for larvae reared at 17 °C until 35 days post-hatching than those growing at 15 °C. Scanning electronic microscopy confirmed that increments are deposited daily, with an average width smaller than 1 µm and as low as 0.33 μm, therefore impossible to distinguish using light microscopy. At colder temperatures, larval otoliths had thinner and less marked increments and lower growth rates, which can lead to incorrect age determinations. The effect of temperature on the otolith microstructure can help in identifying strong temperature gradients experienced by wild sardine larvae.

Retrospective analysis of marine growth and relationships to return rates of Penobscot River Atlantic salmon

Beginning in the 1980s, return rates of Atlantic salmon to the Penobscot River, Maine U.S.A. declined and have persisted at low levels. This downturn coincided with similar declines in North American and European Atlantic salmon stocks and with changes in the Northwest Atlantic ecosystem. Previous studies investigated whether early marine growth explained the declines, but results varied, with decreased growth associated with declines in European stocks but not North American stocks. In this study, we evaluate whether growth over the entire marine stage is related to Atlantic salmon marine survival. We constructed a growth time series from scales of returned Penobscot River Atlantic salmon spanning periods of varying marine survival. We used ANOVA and post-hoc tests to quantify seasonal growth increment differences and principal component analysis to characterize variability among the suite of growth increments. We observed reduced growth during the second winter and second marine year starting in the 1990s, with compensatory seasonal growth relationships. These results indicate that diminished growth during late marine stages is associated with low return rates in this population.

Somatic growth of Atlantic bluefin tuna Thunnus thynnus under global climate variability: Evidence from over 60 years of daily resolved growth increments with a simulation study

Somatic growth is integral to fishery stock productivity. Under climate variability, omitting growth variability renders fishery management strategies non-optimal. Based on a multidecadal tag-recapture database, a case study is presented to investigate the potential growth response of the Atlantic bluefin tuna to three regionally relevant large-scale climate patterns, i.e., the North Atlantic Oscillation, Arctic Oscillation, and Pacific North America pattern. An additional simulation study is conducted to explore the effect of the overall scale and the distribution of measurement error on the detection probability of extrinsic effects and the estimation of growth parameters. Results indicate significant growth response at an intra-annual scale to all three climate indices examined. Identified growth responses to climate variations are highly nonlinear. The projected growth shows increased growth in recent decades under climate variability with respect to the historical mean. Simulation results show a higher probability to detect climate signals when the overall measurement error is low. Substantial bias is expected when the measurement error at tag release is high, cautioning against careless integration of different types of growth data.