Emergent global patterns of ecosystem structure and function from a mechanistic general ecosystem model

Anthropogenic activities are causing widespread degradation of ecosystems worldwide, threatening the ecosystem services upon which all human life depends. Improved understanding of this degradation is urgently needed to improve avoidance and mitigation measures. One tool to assist these efforts is predictive models of ecosystem structure and function that are mechanistic: based on fundamental ecological principles. Here we present the first mechanistic General Ecosystem Model (GEM) of ecosystem structure and function that is both global and applies in all terrestrial and marine environments. Functional forms and parameter values were derived from the theoretical and empirical literature where possible. Simulations of the fate of all organisms with body masses between 10 µg and 150,000 kg (a range of 14 orders of magnitude) across the globe led to emergent properties at individual (e.g., growth rate), community (e.g., biomass turnover rates), ecosystem (e.g., trophic pyramids), and macroecological scales (e.g., global patterns of trophic structure) that are in general agreement with current data and theory. These properties emerged from our encoding of the biology of, and interactions among, individual organisms without any direct constraints on the properties themselves. Our results indicate that ecologists have gathered sufficient information to begin to build realistic, global, and mechanistic models of ecosystems, capable of predicting a diverse range of ecosystem properties and their response to human pressures

Fine-scale movement of juvenile Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) during aggregations in the lower Saint John River Basin, New Brunswick, Canada

Juvenile Atlantic sturgeon form seasonal aggregations near the salt wedge in their natal river systems. We used an array of Vemco Positioning System acoustic receivers to track fine-scale movement within aggregation sites in two rivers in the Saint John River Basin. We used the t-LoCoH convex hull construction algorithm to map space use and aggregation behavior; and nonmetric multidimensional scaling to test for differences between rivers, seasons, and photoperiods. Aggregation sites consisted of small core areas, where juvenile Atlantic sturgeon remained for long periods, that are adjacent to foraging grounds. This structure was largely consistent between rivers and seasons. Directional movement within aggregation sites differed between rivers. In areas of high flow velocity, directional movement was parallel to flow and largely restricted to littoral areas, whereas areas of low flow exhibited no distinct patterns in directional movement. This indicates flow may be an important driver of fine-scale distribution within aggregation sites. Studies of fine-scale space use can inform future investigations of rearing capacity, aid in the identification of critical habitat, and inform management decisions.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Seasonal distribution and movement of juvenile Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) in the lower Saint John River Basin, New Brunswick, Canada

Juvenile Atlantic sturgeon movement and distribution varies seasonally within the lower Saint John River Basin. We use acoustic telemetry to track coarse-scale movement and a network-based approach to develop metrics describing distribution and movement patterns of juvenile Atlantic sturgeon tagged in two rivers, the Saint John and Kennebecasis Rivers. We use principal component analysis to develop indices of movement and residency and test for differences among seasons and between fish from each river. Juvenile Atlantic sturgeon exhibit higher residency during summer months compared to winter and spring. Juveniles are primarily concentrated in the brackish waters of the lower river reaches but make movements as far upriver as rkm 88. There was high variation in distribution and movement patterns exhibited by fish tagged in the Kennebecasis River, ranging from single-location occupancy to wide distribution. Three fish left the system during the study, indicating juveniles embark on brief marine excursions. Identifying spatiotemporal distributions of juvenile Atlantic sturgeon in their natal river systems is a crucial step towards identifying critical habitat and informing management decisions for this species.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Experimental examination of surgical procedures for implanting sonic transmitters in juvenile shortnose sturgeon and Atlantic sturgeon

Acoustic telemetry has become a leading tool for monitoring the movements of and habitat use by many sturgeon species worldwide; however, procedures for internal tagging of small juvenile sturgeon (<55 cm TL) are lacking. We examined effects of implantation technique on growth, tag retention, and survival of juvenile (<55 cm) Shortnose Sturgeon Acipenser brevirostrum and Atlantic Sturgeon A. oxyrinchus by using dummy acoustic tags. Two implantation techniques were used: (1) anchoring the tag to the wall of the peritoneal cavity and (2) no internal anchoring of the tag. These treatment groups were compared with two control groups: fish that received anesthetic only and fish that received anesthetic and an incision. Retention rate was significantly higher for anchored tags (88%) than for nonanchored tags (25%) in Shortnose Sturgeon juveniles, while Atlantic Sturgeon juveniles retained 100% of tags regardless of treatment. Nonanchored tags that were lost during the second week were expelled through the incision site, whereas later tag expulsions (during weeks 7 and 8) occurred through the anus. There was no significant difference in absolute growth and specific growth rates between the treatment groups throughout the 8-week study for either species. Growth of both species was significantly lower in the first week after surgery but increased and remained constant for the remainder of the experiment. Use of nonanchored tags significantly increased incision healing times for both species; however, Atlantic Sturgeon healed significantly faster (35 d) than Shortnose Sturgeon (42 d). No mortality occurred in any of the treatment groups. Results of this study suggest that juvenile Shortnose Sturgeon and Atlantic Sturgeon can undergo internal tag implantation resulting in long retention times with largely unaffected growth and no mortality

Growth, survivorship, and predator avoidance capability of larval shortnose sturgeon (Acipenser brevirostrum) in response to delayed feeding.

Larval shortnose sturgeon, reared at 17°C, were subjected to delayed feeding treatments of 0, 5, 10, 15, 18, and 23 days post-yolk absorption to examine effects of food deprivation on growth, survival, swimming activity, and escape capabilities. Starvation affected growth and survival but despite degree of starvation, larvae were able to resume growth and experience high survivorship following feeding. Specific growth rate based on larval dry weight for the period directly following first feeding was highest for the day 15 and 18 delayed feeding treatments. There were no differences in survival between the 0 and 5 day treatments, however survival was reduced to 71.2%, 45.4%, and 28.8% for 10, 15, and 18 day delayed feeding treatments, respectively. Shortnose sturgeon had a point-of-no-return (PNR; 55.7% initiated feeding) at ~19 days (or 42 days post-fertilization) following the full absorption of yolk. Mean percent swimming activity and swimming speeds showed an interaction between delayed feeding treatment and larval age, such that no differences were detected at 1 and 6 days post-yolk absorption, while these swimming behaviors generally increased or spiked as feeding was delayed for 10, 15, and 18 days post-yolk absorption. At 23 days post-yolk absorption, only swimming speed increased for larvae that were denied food for 18 days. While there was an interaction between delayed feeding treatments and age for proportion of larvae exhibiting an escape response, generally, larvae from all feeding treatments exhibited a positive escape response. There were also interactions between delayed feeding treatments and age post-yolk absorption for mean and maximum escape speeds, such that less aggressive escape responses were typically detected the longer larvae were denied food. Our research suggests that larval shortnose sturgeon increase physical activity during periods of starvation to find a food patch while remaining vigilant but maybe not as capable to defend against a predatory attack as fed individuals

Frizzled 4 regulates ventral blood vessel remodeling in the zebrafish retina

Familial exudative vitreoretinopathy (FEVR) is a rare congenital disorder characterized by a lack of blood vessel growth to the periphery of the retina with secondary fibrovascular proliferation at the vascular-avascular junction. These structurally abnormal vessels cause leakage and hemorrhage, while the fibroproliferative scarring results in retinal dragging, detachment and blindness. Mutations in the FZD4 gene represent one of the most common causes of FEVR. A loss of function mutation resulting from a 10-nucleotide insertion into exon 1 of the zebrafish fzd4 gene was generated using transcription activator-like effector nucleases (TALENs). Structural and functional integrity of the retinal vasculature was examined by fluorescent microscopy and optokinetic responses. Zebrafish retinal vasculature is asymmetrically distributed along the dorsoventral axis, with active vascular remodeling on the ventral surface of the retina throughout development. fzd4 mutants exhibit disorganized ventral retinal vasculature with discernable tubular fusion by week 8 of development. Furthermore, fzd4 mutants have impaired optokinetic responses requiring increased illumination. We have generated a visually impaired zebrafish FEVR model exhibiting abnormal retinal vasculature. These fish provide a tractable system for studying vascular biology in retinovascular disorders, and demonstrate the feasibility of using zebrafish for evaluating future FEVR genes identified in humans. This article is protected by copyright. All rights reserved