2006. A comparison of the species Á/time relationship across ecosystems and taxonomic groups. Á/ Oikos 112: 185 Á/195.The species Á/time relationship (STR) describes how the species richness of a community increases with the time span over which the community is observed. This pattern has numerous implications for both theory and conservation in much the same way as the species Á/area relationship (SAR). However, the STR has received much less attention and to date only a handful of papers have been published on the pattern. Here we gather together 984 community time-series, representing 15 study areas and nine taxonomic groups, and evaluate their STRs in order to assess the generality of the STR, its consistency across ecosystems and taxonomic groups, its functional form, and its relationship to local species richness. In general, STRs were surprisingly similar across major taxonomic groups and ecosystem types. STRs tended to be well fit by both power and logarithmic functions, and power function exponents typically ranged between 0.2 and 0.4. Communities with high richness tended to have lower STR exponents, suggesting that factors increasing richness may simultaneously decrease turnover in ecological systems. Our results suggest that the STR is as fundamental an ecological pattern as the SAR, and raise questions about the general processes underlying this pattern. They also highlight the dynamic nature of most species assemblages, and the need to incorporate time scale in both basic and applied research on species richness patterns.

One of the most commonly predicted effects of global ocean warming on marine communities is a poleward shift in the distributional boundaries of species with an associated replacement of cold‐water species by warm‐water species. However, these types of predictions are imprecise and based largely on broad correlations in uncontrolled studies that examine changes in the distribution or abundances of species in relation to seawater temperature. Our study used an 18‐year sampling program in intertidal and subtidal habitats and before–after, control–impact analyses. We show that a 3.5°C rise in seawater temperature, induced by the thermal outfall of a power‐generating station, over 10 years along 2 km of rocky coastline in California resulted in significant community‐wide changes in 150 species of algae and invertebrates relative to adjacent control areas experiencing natural temperatures. Contrary to predictions based on current biogeographic models, there was no trend toward warmer‐water species with southern geographic affinities replacing colder‐water species with northern affinities. Instead, the communities were greatly altered in apparently cascading responses to changes in abundance of several key taxa, particularly habitat‐forming subtidal kelps and intertidal foliose red algae. Many temperature‐sensitive algae decreased greatly in abundance, whereas many invertebrate grazers increased. The responses of these benthic communities to ocean warming were mostly unpredicted and strongly coupled to direct effects of temperature on key taxa and indirect effects operating through ecological interactions.

A three-dimensional, near real-time data-assimilative modeling system for the California coastal ocean is presented. The system consists of a Regional Ocean Modeling System (ROMS) forced by the North American Mesoscale Forecast System (NAM). The ocean model has a horizontal resolution of approximately three kilometers and utilizes a multi-scale three-dimensional variational (3DVAR) data assimilation methodology. The system is run in near real-time to produce a nowcast every six hours and a 72-hour forecast every day. The performance of this nowcast system is presented using results from a six-year period of 2009-2015. The ROMS results are first compared with the assimilated data as a consistency check. RMS differences in observed satellite infrared sea surface temperatures (SST) and vertical profiles of temperature between observations and ROMS nowcasts were found to be mostly less than 0.5 °C, while the RMS differences in vertical profiles of salinity between observations and ROMS nowcasts were found to be 0.09 or less. The RMS differences in SST show a distinct seasonal cycle that mirrors the number of observations available: the nowcast is less skillful with larger RMS differences during the summer months when there are less infrared SST observations due to the presence of low-level clouds. The larger differences during summer were found primarily along the northern and central coasts in upwelling regions where strong gradients exist between colder upwelled waters nearshore and warmer offshore waters. RMS differences between HF radar surface current observations and ROMS nowcasts were approximately 7-8 cm s −1 , which is about 30% of the time mean current speeds in this region. The RMS differences in sea surface height (SSH) between the AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic) altimetric satellite observations and ROMS nowcasts were about 2 cm. In addition, the system realistically reproduces the interannual variability in temperatures at the M1 mooring (122.03°W, 36.75°N) in Monterey Bay, including the strong warming of the California coastal ocean during 2014. The ROMS nowcasts were then validated against independent observations. A comparison of the ROMS nowcast with independent profile observations of temperature and salinity shows RMS differences of 0.7 to 0.92 °C and 0.13 to 0.17, which are larger (by up to a factor of 2) than the differences found in the comparisons with assimilated data. Validation of the depth-averaged currents derived from Spray gliders shows that the flow patterns associated with California Current and California Undercurrent/Davidson current systems and their seasonal variations are qualitatively reproduced by the ROMS modeling system. Lastly, the impact of two recent upgrades to the system is quantified. Switching the lateral boundary conditions from a U.S. west coast regional model to the global HYCOM (HYbrid Coordinate Ocean Model) model results in an improvement in the simulation of the seasonal and interannual variations in the SSH, especiall...

Executive SummaryDuring 2007, the U.S. Army Corps of Engineers (USACE) contracted Pacific Northwest National Laboratory (PNNL) to evaluate smolt responses to hydrodynamic conditions at surface flow outlets at McNary and The Dalles dams. This study provides information about juvenile salmonid behaviors at the two dams that USACE, fisheries resource managers, and others can use to support decisions about longterm measures to enhance fish passage. The goal of the study was to use fish behavioral responses to ambient flow fields to support general design guidelines for hydraulic conditions that readily pass juvenile salmon at surface flow outlets (SFOs). The study is also applicable to bioengineering for juvenile salmonid passage at irrigation diversions, tide gates, and culverts. We integrated data about smolt movements and hydrodynamic conditions at SFOs at McNary and The Dalles dams during 2007 to address the following questions: Which hydraulic variables are most strongly associated with fish behavioral responses? Of these, are there threshold levels that could be used to support SFO design guidelines?  The Dalles Dam -Apply new empirical data from simultaneous remote sensing techniques and computational fluid dynamics (CFD) modeling in the nearfield of the sluiceway to accomplish the following:: Objectives1. Characterize fish behavior and water velocity patterns.2. Examine descriptive and statistical associations between juvenile salmonid movements and hydrodynamic conditions immediately upstream of the SFO entrances.3. Address guidelines for hydraulic parameters of the flow net upstream of the SFO that would be conducive to juvenile salmonids passing into the SFO entrance. MethodsIn the field, we collected simultaneous data from an acoustic Doppler current profiler (ADCP) and a dual-frequency identification sonar (DIDSON). The ADCP and DIDSON acoustic beams were oriented to sample overlapping water volumes. At McNary Dam, the equipment was deployed upstream of the TSW at Bay 19. At The Dalles Dam, the instruments were deployed upstream off the face of the dam to sample in the nearfield (< 20 m) of Sluices 1-1 and 1-2 during six 4-day sampling episodes. The main drawback of the ADCP, however, is that the size of its sample volume can be large (meters) relative to the size of the fish (centimeters); this factor increases as range increases. Therefore, we supplemented the study at The Dalles with CFD modeling for a scenario with consistent dam operations in the vicinity Smolt Responses to Hydrodynamics, 2007 Final Report iv (Main Units 1 through 4) of the DIDSON sample volume. The CFD modeling allowed for capture of fine-scale spatial resolution, but it was steady-state temporally. We merged the water and fish data sets to calculate the fish effort variables (Figure ES.1) that are elemental to this study. Comparison of the ADCP and CFD results revealed an apparent problem with our application of the ADCP. The instrument was functioning properly, but the assumption that water currents were sufficiently homogen...

Despite the recognition of the usefulness of BACI designs for assessing environmental impacts, there are few examples because of the need for repetitive sampling over long time periods. Our examination of the application of a BACI design to detect the impacts of elevated seawater temperature from the Diablo Canyon Power Plant in central California on rocky intertidal communities showed statistically significant changes in a large percentage of the species analyzed. The statistical power of the analysis resulted from both the large numbers of surveys before and during plant operation and from other design features that made the study resilient to the effects of two ''100-year'' storms, several ENSO warming events, and the highly variable nature of the impacts. The large data set from the study required the development of decision rules for determining the appropriate surveys, stations, and species to analyze. BACI analyses were used to test the effects of the thermal plume on 47 algal and 50 invertebrate data sets. There were statistically significant effects for 79% of the algal and 60% of the invertebrate data sets. At the impact sites, there was a loss of cover by foliose algae and increases in crustose forms. Many invertebrates, particularly grazing gastropods, increased in abundance. Multivariate analysis of the community showed that there was continual change in impact sites that lasted throughout the study. The nature, magnitude, and spatial extent of the effects identified from the study are being used to determine appropriate plant modifications or mitigation for the effects of discharge. This study illustrates many of the problems in analyzing environmental effects and clearly demonstrates the need for long-term monitoring. This was especially true for this study, where storms and ENSO events affected our ability to analyze data from some of the stations, and points out the importance of having redundancies built into monitoring programs. The complex interactions among the direct effects of the discharge, indirect community-level effects, and variation due to oceanographic conditions provide useful insights for planning impact assessments and other ecological studies, and help contribute toward science-based regulation and management.