A Model of Genome Size Evolution for Prokaryotes in Stable and Fluctuating Environments

Temporal variability in ecosystems significantly impacts species diversity and ecosystem productivity and therefore the evolution of organisms. Different levels of environmental perturbations such as seasonal fluctuations, natural disasters, and global change have different impacts on organisms and therefore their ability to acclimatize and adapt. Thus, to understand howorganisms evolve under different perturbations is a key for predicting how environmental change will impact species diversity and ecosystem productivity. Here, we developed a computer simulation utilizing the individual-based model approach to investigate genome size evolution of a haploid, clonal and free-living prokaryotic population across different levels of environmental perturbations. Our results showthat a greater variability of the environment resulted in genomes with a larger number of genes. Environmental perturbations were more effectively buffered by populations of individuals with relatively large genomes. Unpredictable changes of the environment led to a series of population bottlenecks followed by adaptive radiations. Our model shows that the evolution of genome size is indirectly driven by the temporal variability of the environment. This complements the effects of natural selection directly acting on genome optimization. Furthermore, species that have evolved in relatively stable environments may face the greatest risk of extinction under global change as genome streamlining genetically constrains their ability to acclimatize to the new environmental conditions, unless mechanisms of genetic diversification such as horizontal gene transfer will enrich their gene pool and therefore their potential to adapt

Florida Bay Science Program: a synthesis of research on Florida Bay

This report documents the progress made toward the objectives established in the Strategic Plan revised in 1997 for the agencies cooperating in the program. These objectives are expressed as five questions that organized the research on the Florida Bay ecosystem: Ecosystem History What was the Florida Bay ecosystem like 50, 100, and 150 years ago? Question 1—Physical Processes How and at what rates do storms, changing freshwater flows, sea level rise, and local evaporation and precipitation influence circulation and salinity patterns within Florida Bay and exchange between the bay and adjacent waters? Question 2—Nutrient Dynamics What is the relative importance of the influx of external nutrients and of internal nutrient cycling in determining the nutrient budget for Florida Bay? What mechanisms control the sources and sinks of the bay’s nutrients? Question 3—Plankton Blooms What regulates the onset, persistence, and fate of planktonic algal blooms in Florida Bay? Question 4—Seagrass Ecology What are the causes and mechanisms for the observed changes in the seagrass community of Florida Bay? What is the effect of changing salinity, light, and nutrient regimes on these communities? Question 5—Higher Trophic Levels What is the relationship between environmental and habitat change and the recruitment, growth, and survivorship of animals in Florida Bay? Each question examines different characteristics of the Florida Bay ecosystem and the relation of these to the geomorphological setting of the bay and to processes linking the bay with adjacent systems and driving change.This report also examines the additional question of what changes have occurred in Florida Bay over the past 150 years

Tidal stirring and phytoplankton bloom dynamics in an estuary

A decade of observation in South San Francisco Bay demonstrates that estuarine phytoplankton biomass fluctuates at the time scale of days to weeks, and that much of this variability is associated with fluctuations in tidal energy. During the spring seasons of every year from 1980–1990, episodic blooms occurred in which phytoplankton biomass rose from a baseline of 2–4 mg chlorophyll a m–3, peaked at 20–40 mg chlorophyll a m–3, and then returned to baseline values, all within several weeks. Each episode of biomass increase occurred during neap tides, and each bloom decline coincided with spring tides. This suggests that daily variations in the rate of vertical mixing by tidal stirring might control phytoplankton bloom dynamics in some estuaries. Simulation experiments with a numerical model of phytoplankton population dynamics support this hypothesis. The model incorporates biological processes (light-dependent growth, zooplankton grazing, benthic grazing) and physical processes (sinking, vertical mixing) as controls on the biomass distribution of phytoplankton in a 10-m water column. Numerical simulations indicate that phytoplankton dynamics are highly sensitive to the rate of vertical mixing (parameterized as an eddy diffusivity Kz), such that biomass increases rapidly at small Kz (5 m2 d–1), but not at large Kz (50 m2 d–1). Cyclic variation of Kz between 5 and 50 over a 14-d period (simulated neap-spring cycle) yields simulation results that are similar to bloom events observed in this estuary

Immigration and early life stages recruitment of the European flounder (Platichthys flesus) to an estuarine nursery: the influence of environmental factors

Connectivity between coastal spawning grounds and estuarine nurseries is a critical step in the life cycle of many fish species. Larval immigration and transport-associated physical–biological processes are determinants of recruitment success to nursery areas. The recruitment of the European flounder, Platichthys flesus, to estuarine nurseries located at the southern edge of the species distribution range, has been usually investigated during its juvenile stages, while estuarine recruitment during the earlier planktonic life stage remains largely unstudied. The present study investigated the patterns of flounder larval recruitment and the influence of environmental factors on the immigration of the early life stages to the Lima estuary (NW Portugal), integrating data on fish larvae and post-settlement individuals (< 50 mm length), collected over 7 years. Late-stage larvae arrived at the estuary between February and July and peak abundances were observed in April. Post-settlement individuals (< 50 mm) occurred later between April and October, whereas newly-settled ones (< 20 mm) were found only in May and June. Variables associated with the spawning, survival and growth of larvae in the ocean (sea surface temperature, chlorophyll a and inland hydrological variables) were the major drivers of flounder occurrence in the estuarine nursery. Although the adjacent coastal area is characterized by a current system with strong seasonality and mesoscale variability, we did not identify any influence of variables related with physical processes (currents and upwelling) on the occurrence of early life stages in the estuary. A wider knowledge on the influence of the coastal circulation variability and its associated effects upon ocean-estuarine connectivity is required to improve our understanding of the population dynamics of marine spawning fish that use estuarine nurseries

Changes in the Lower Chesapeake Bay Food-Chain in Presence of the Sea Nettle Chrysaora-quinquecirrha (Scyphomedusa)

The abundance of 4 levels of the lower Chesapeake Bay food chain (Chlorophyll a, herbivores, ctenophore Mnemiopsis leidyi, and Scyphomedusa Chrysaora quinquecirrha) were moni­tored twice weekly at 4 stations from May 10 through Sep 30, 1982 in the Lafayette and Elizabeth Rivers (Virginia). The herbivore standing stock, largely copepods, declined sharply in late May when M. Jeidyi appeared, but rebounded a month later when C. quinquecirrha medusae reduced the ctenophore population. Despite the additional presence of Aurelia aurita (Scyphomedusa) from Jul onward, herbivore abundance remained at moderate levels until the end of the study period. Phytoplankton abundance fluctuated and may have been responsible for brief periods of food shortage; however, the major periods of low herbivore abundance do not seem to have been kept low by food limitation. M. Jeidyi made a modest resurgence in late Aug when the C. quinquecirrha population underwent its seasonal decline. Our data suggest that C. quinquecirrha contributes to the secondary productivity of the lower Chesapeake Bay by controlling M. leidyi during summer

ENSO-Induced Co-Variability of Salinity, Plantkton Biomass and Coastal Currents in the Northern Gulf of Mexico

The northern Gulf of Mexico (GoM) is a region strongly influenced by river discharges of freshwater and nutrients, which promote a highly productive coastal ecosystem that host commercially valuable marine species. A variety of climate and weather processes could potentially influence the river discharges into the northern GoM. However, their impacts on the coastal ecosystem remain poorly described. By using a regional ocean-biogeochemical model, complemented with satellite and in situ observations, here we show that El Niño - Southern Oscillation (ENSO) is a main driver of the interannual variability in salinity and plankton biomass during winter and spring. Composite analysis of salinity and plankton biomass anomalies shows a strong asymmetry between El Niño and La Niña impacts, with much larger amplitude and broader areas affected during El Niño conditions. Further analysis of the model simulation reveals significant coastal circulation anomalies driven by changes in salinity and winds. The coastal circulation anomalies in turn largely determine the spatial extent and distribution of the ENSO-induced plankton biomass variability. These findings highlight that ENSO-induced changes in salinity, plankton biomass, and coastal circulation across the northern GoM are closely interlinked and may significantly impact the abundance and distribution of fish and invertebrates

Circulation, Vol. 14, No. 1

Summer 2007 issue of CCPO Circulation featuring article Air-Sea Measurements in the Indian Ocean by Dr. Brian Wardhttps://digitalcommons.odu.edu/ccpo_circulation/1014/thumbnail.jp

Water Resources and Environment Assessment in River Basin based on Hydro-BEAM

本年度はHydro-BEAM に付加するモジュール及び評価の側面についていくつか検討している。主なものは，水量・水質・生態環境を組み入れた流域水環境モデル，侵食・堆積環境と魚類の生息場，ダム下流流程と浮遊有機物動態，地表面条件とそれが積雲・降雨に及ぼす影響，地球温暖化と流域水資源環境への影響評価，である。In this fiscal year (FY2005), some modules to be added to Hydro-BEAM and some aspects of evaluation have been discussed. Following items are the main topics and included in this report. 1) Regional water circulation processes with water quantity, quality, and ecosystem 2) Difference in habitat preference of Rhinogobius flumineus among erosional and depositional reaches 3) Variation in drift distance of suspended POM in relation to flow regimes and channel geomorphology 4) Effect of land surface condition on convective precipitation over the mountainous region in Lake Biwa during the summer season 5) Impact assessment on water resources environment in river basin due to global warming本年度はHydro-BEAM に付加するモジュール及び評価の側面についていくつか検討している。主なものは，水量・水質・生態環境を組み入れた流域水環境モデル，侵食・堆積環境と魚類の生息場，ダム下流流程と浮遊有機物動態，地表面条件とそれが積雲・降雨に及ぼす影響，地球温暖化と流域水資源環境への影響評価，である。In this fiscal year (FY2005), some modules to be added to Hydro-BEAM and some aspects of evaluation have been discussed. Following items are the main topics and included in this report. 1) Regional water circulation processes with water quantity, quality, and ecosystem 2) Difference in habitat preference of Rhinogobius flumineus among erosional and depositional reaches 3) Variation in drift distance of suspended POM in relation to flow regimes and channel geomorphology 4) Effect of land surface condition on convective precipitation over the mountainous region in Lake Biwa during the summer season 5) Impact assessment on water resources environment in river basin due to global warmin

3D Computer Modeling Offers New Insights Into Diatom Ecology

Algae supply over half of the Earth’s global primary production and form the base of almost all aquatic food networks. Thus, changes in algal productivity or composition will induce profound shifts in many ecosystems. This research is guided by two questions. Herein I ask if 3D models of algae can be created accurately enough to use for research applications? If they can be accurately created, then how can these models be used to advance our understanding of functional trait evolution and paleoecology? Herein, I develop 3D computer models for estimating the volume of individual algae and their parts. I also examine pressures that influence algae biomass, resource requirements, and trait evolution. Further, I apply these to an annually resolved sediment records to reveal paleontological applications that can be used to reconstruct past ecosystems and evolutionary events. This dissertation provides the means improve historical ecological reconstructions, advance predictions of ecological changes that will occur under global climate change and allow for evolutionary cost benefit analysis of traits of microscopic organisms. For this study I exploit the sedimentary record from Herd Lake Idaho USA (44.089428, -114.173921). because it contains large (~0.5 cm) annual layers. These layers are extraordinarily abundant in the remains of the diatom Stephanodiscus niagarae. These qualities present an ideal setting to produce accurate 3D computer models of a diatom that influences a large portion of the nutrient cycles in an aquatic system. The abundance of individuals provides ample data and diversity for strong statistical interpretations of the diatom populations while the annual resolution of the sediment provides a means to compare the novel methods to weather and climate data that inform us of the ecological significance of these new methods. The bounds of this study are within the years 1927 – 2011 and pertain to aquatic environments on Earth. Although these works are constrained to the recent past and local ecosystems, future applications are bound only by the geological time frame in which algae have existed and are limited in space to wherever algae are found in the universe