Herbivore effects increase with latitude across the extent of a foundational seagrass

Climate change is altering the functioning of foundational ecosystems. While the direct effects of warming are expected to influence individual species, the indirect effects of warming on species interactions remain poorly understood. In marine systems, as tropical herbivores undergo poleward range expansion, they may change food web structure and alter the functioning of key habitats. While this process ('tropicalization') has been documented within declining kelp forests, we have a limited understanding of how this process might unfold across other systems. Here we use a network of sites spanning 23° of latitude to explore the effects of increased herbivory (simulated via leaf clipping) on the structure of a foundational marine plant (turtlegrass). By working across its geographic range, we also show how gradients in light, temperature and nutrients modified plant responses. We found that turtlegrass near its northern boundary was increasingly affected (reduced productivity) by herbivory and that this response was driven by latitudinal gradients in light (low insolation at high latitudes). By contrast, low-latitude meadows tolerated herbivory due to high insolation which enhanced plant carbohydrates. We show that as herbivores undergo range expansion, turtlegrass meadows at their northern limit display reduced resilience and may be under threat of ecological collapse.

Microbiomes of Thalassia testudinum throughout the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico are influenced by site and region while maintaining a core microbiome

Plant microbiomes are known to serve several important functions for their host, and it is therefore important to understand their composition as well as the factors that may influence these microbial communities. The microbiome of Thalassia testudinum has only recently been explored, and studies to-date have primarily focused on characterizing the microbiome of plants in a single region. Here, we present the first characterization of the composition of the microbial communities of T. testudinum across a wide geographical range spanning three distinct regions with varying physicochemical conditions. We collected samples of leaves, roots, sediment, and water from six sites throughout the Atlantic Ocean, Caribbean Sea, and the Gulf of Mexico. We then analyzed these samples using 16S rRNA amplicon sequencing. We found that site and region can influence the microbial communities of T. testudinum, while maintaining a plant-associated core microbiome. A comprehensive comparison of available microbial community data from T. testudinum studies determined a core microbiome composed of 14 ASVs that consisted mostly of the family Rhodobacteraceae. The most abundant genera in the microbial communities included organisms with possible plant-beneficial functions, like plant-growth promoting taxa, disease suppressing taxa, and nitrogen fixers.

Global inventory of species categorized by known underwater sonifery

A working group from the Global Library of Underwater Biological Sounds effort collaborated with the World Register of Marine Species (WoRMS) to create an inventory of species confirmed or expected to produce sound underwater. We used several existing inventories and additional literature searches to compile a dataset categorizing scientific knowledge of sonifery for 33,462 species and subspecies across marine mammals, other tetrapods, fishes, and invertebrates. We found 729 species documented as producing active and/or passive sounds under natural conditions, with another 21,911 species deemed likely to produce sounds based on evaluated taxonomic relationships. The dataset is available on both figshare and WoRMS where it can be regularly updated as new information becomes available. The data can also be integrated with other databases (e.g., SeaLifeBase, Global Biodiversity Information Facility) to advance future research on the distribution, evolution, ecology, management, and conservation of underwater soniferous species worldwide.

The importance of context in the acoustic behaviors of marine, subtropical fish speciesa)

Despite the importance of acoustic signaling in fishes, the prevalence of the behavioral contexts associated with their active (i.e., intentional) sound production remains unclear. A systematized review was conducted to explore documented acoustic behaviors in marine, subtropical fishes and potential influences affecting their relative pervasiveness. Data were collected on 186 actively soniferous fish species studied across 194 publications, identified based on existing FishSounds and FishBase datasets. Disturbance was the most common behavioral context associated with active sound production-reported for 140 species or 75% of the species studied-and then aggression (n = 46 species, 25%) and reproduction (n = 34 species, 18%). This trend, however, somewhat differed when examined by research effort, study environment, and fish family, such as reproductive sounds being more commonly reported by studies conducted in the wild. The synthesis of fish sound production behaviors was in some ways stymied by the fact that many species' sound production did not have discernible associated behavioral contexts and that some investigations did not clearly identify the study environments in which active sound production was observed. These findings emphasize the importance of context-behavioral or otherwise-when studying acoustic behaviors in fishes.

Submerged Aquatic Vegetation Species and Populations Within Species Respond Differently to Environmental Stressors Common in Restorations

Submerged aquatic vegetation (SAV) improves environmental conditions by acting as a sediment stabilizer and nutrient retention tool; therefore, reintroduction of SAV is a common freshwater restoration goal. Initial plant establishment is often difficult in suboptimal conditions, and planting material with specific traits may increase establishment rates. Here we evaluate the variability in plant traits based on collection location. We find consistent differences in traits of plants collected from different natural water bodies, and those differences persist in plants grown from seeds under common garden greenhouse conditions-presumably because of genetic differentiation. In three separate mesocosm experiments, we tested the interactive impacts of collection location and environmental condition (control conditions, reduced light, elevated nutrients, or a combination of reduced light and elevated nutrients) on plant reproduction and on traits that might indicate future restoration success (plant height, number of leaves, and rhizome diameter). In most cases, plant traits at the end of the experiments varied by collection location, environmental condition, and an interaction between the two. The best performing plants also depended on response variable (e.g., plant height or number of new shoots produced). Together these results suggest that unpredictable environmental conditions at restoration sites will make selection of a single high-performing plant source difficult, so we suggest incorporating a diverse set of collection locations to increase the probability of incorporating desirable traits.

Submerged Aquatic Vegetation Patch Size Affects Fish Communities in a Turbid-Algal Lake

Submerged aquatic vegetation (SAV) is declining worldwide, leading to subsequent reductions in the ecological functions associated with SAV in shallow aquatic ecosystems, including providing habitat for fishes. Extensive restoration efforts are required to reverse this trend, but studies focusing on aquatic vegetation have been uncommon in recent years relative to other primary producers. Evaluations of the most beneficial SAV species and characteristics for fishes are especially rare. Because of the potentially complex and inconsistent responses of fish to different management actions, further research is necessary to evaluate the species-specific and community-level effects of SAV to inform restoration decision-making. To examine what SAV characteristics increase fish habitat use in a turbid-algal lake undergoing restoration, we sampled 29 areas around Lake Apopka, Florida (USA) with fyke nets and trotlines. We examined the impact of eight environmental variables on fish abundance, biomass, community structure, and predation potential. For each approximated 0.6 m2 increase in SAV patch size, total fish biomass catch increased 6.5 g hr−1. Fish community composition based on abundance also changed with an increase in SAV patch size. The number of bait items missing from trotlines, a measure of predation potential, was most affected by water temperature, wind speed, and time of day, but not by the SAV variables tested. These results expand existing knowledge of fish habitat use of SAV and will inform future management efforts to conserve and restore fish communities by focusing on specific SAV characteristics such as patch size.

Temporal stability in patterns of genetic diversity and structure of a marine foundation species (Zostera marina)

Genetic diversity and population structure reflect complex interactions among a diverse set of processes that may vary temporally, limiting their potential to predict ecological and evolutionary outcomes. Yet, the stability of these patterns is rarely tested. We resampled eelgrass (Zostera marina) meadows from published studies to determine variability in genetic diversity and structure within and between meadows over 5-12 years. The meadows sampled (San Francisco, Tomales and Bodega Bays in California and the Virginia coastal bays) represent a range of life histories (annual vs perennial), age (well-established vs restored) and environments (rural vs urbanized). In all of these systems, neither diversity nor differentiation (F_ST) changed over time. Differences among tidal heights within Bodega Bay were also remarkably consistent, with the high intertidal being more diverse than the subtidal, and tidal height differentiation being modest but significant at both time points. Historical studies used only a few microsatellite loci; therefore, our temporal comparisons were based on 4-5 loci. However, analysis of the current data using a set of 12 loci show that 4-5 loci are sufficient to describe diversity and differentiation patterns in this system. This temporal consistency was not because of the resampling of large clones, underscoring the feasibility and relevance of understanding drivers of the differences. Because seagrasses are declining at rapid rates, restoration and conservation are increasingly a coastal management priority. Our results argue that surveys of eelgrass genetic structure and diversity at decadal scales can provide accurate depictions of populations, increasing the utility of published genetic data for restoration and designing networks of reserves.

Response of a Habitat-Forming Marine Plant to a Simulated Warming Event Is Delayed, Genotype Specific, and Varies with Phenology

Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of warming events increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate warming event of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass). We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14–15°C, but extended warming periods of 17–18°C occur episodically. Experimental warming increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of warming on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been warmed. While all genotypes’ production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control) were the most susceptible to the detrimental effects of warming. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species’ thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient frequency of warming or other stress events.

Conservation of eelgrass (Zostera marina) genetic diversity in a mesocosm-based restoration experiment

Eelgrass (Zostera marina) forms the foundation of an important shallow coastal community in protected estuaries and bays. Widespread population declines have stimulated restoration efforts, but these have often overlooked the importance of maintaining the evolutionary potential of restored populations by minimizing the reduction in genetic diversity that typically accompanies restoration. In an experiment simulating a small-scale restoration, we tested the effectiveness of a buoy-deployed seeding technique to maintain genetic diversity comparable to the seed source populations. Seeds from three extant source populations in San Francisco Bay were introduced into eighteen flow-through baywater mesocosms. Following seedling establishment, we used seven polymorphic microsatellite loci to compare genetic diversity indices from 128 shoots to those found in the source populations. Importantly, allelic richness and expected heterozygosity were not significantly reduced in the mesocosms, which also preserved the strong population differentiation present among source populations. However, the inbreeding coefficient F_IS was elevated in two of the three sets of mesocosms when they were grouped according to their source population. This is probably a Wahlund effect from confining all half-siblings within each spathe to a single mesocosm, elevating F_IS when the mesocosms were considered together. The conservation of most alleles and preservation of expected heterozygosity suggests that this seeding technique is an improvement over whole-shoot transplantation in the conservation of genetic diversity in eelgrass restoration efforts.

Genetic diversity enhances restoration success by augmenting ecosystem services

Disturbance and habitat destruction due to human activities is a pervasive problem in near-shore marine ecosystems, and restoration is often used to mitigate losses. A common metric used to evaluate the success of restoration is the return of ecosystem services. Previous research has shown that biodiversity, including genetic diversity, is positively associated with the provision of ecosystem services. We conducted a restoration experiment using sources, techniques, and sites similar to actual large-scale seagrass restoration projects and demonstrated that a small increase in genetic diversity enhanced ecosystem services (invertebrate habitat, increased primary productivity, and nutrient retention). In our experiment, plots with elevated genetic diversity had plants that survived longer, increased in density more quickly, and provided more ecosystem services (invertebrate habitat, increased primary productivity, and nutrient retention). We used the number of alleles per locus as a measure of genetic diversity, which, unlike clonal diversity used in earlier research, can be applied to any organism. Additionally, unlike previous studies where positive impacts of diversity occurred only after a large disturbance, this study assessed the importance of diversity in response to potential environmental stresses (high temperature, low light) along a water-depth gradient. We found a positive impact of diversity along the entire depth gradient. Taken together, these results suggest that ecosystem restoration will significantly benefit from obtaining sources (transplants or seeds) with high genetic diversity and from restoration techniques that can maintain that genetic diversity.

The efficacy of a response cost-based treatment package for managing aggressive behavior in preschoolers

The present study examined the effectiveness of a response cost treatment package for improving the classroom behavior of four aggressive preschoolers. Using a multiple baseline design, teachers implemented the response cost system during the treatment phases of the study. The system required teachers to remove smiley faces contingent on aggressive behavior. Each face loss was accompanied by a reprimand. If the child retained at least one smiley face at the end of the observation period, he was allowed to choose from a list of rewards. Rewards were easily administered at school. The results indicated that the response cost treatment package substantially decreased aggressive behavior and was a highly acceptable classroom treatment to teachers and parents.

Plasma B6 vitamer and plasma and urinary 4-pyridoxic acid concentrations of middle-aged obese black women

Plasma B6 vitamer and plasma and urinary 4-pyridoxic acid (4-PA) concentrations of fifteen middle-aged obese black women were determined by high-performance liquid chromatography (HPLC). Estimated protein and vitamin B6 intakes of the subjects, aged 27-52 years, were 64.5 +/- 15.6 g and 1.21 +/- 0.68 mg (mean +/- S.D.), respectively. Mean HPLC-derived plasma B6 vitamer and 4-PA concentrations for these subjects were 68.9, 3.1, 1.2, 4.1, 3.4, 7.2 and 2.0 nmol/l for pyridoxal 5'-phosphate (PLP), pyridoxine 5'-phosphate, pyridoxamine 5'-phosphate, pyridoxal, pyridoxine, pyridoxamine and 4-PA, respectively. The mean urinary 4-PA/creatinine ratio of the women was 0.88 mumol/mmol. All subjects had plasma PLP levels indicative of adequate vitamin B6 status. Vitamin B6 status parameters of the middle-aged obese black women were similar to those previously reported for white nonobese women having adequate vitamin B6 status.

Plasma pyridoxal 5'-phosphate concentrations in obese and nonobese black women residing near Petersburg, VA

The vitamin B-6 status of 15 obese and 15 nonobese black women aged 21-51 y who were not taking vitamin supplements was assessed by using plasma pyridoxal 5'-phosphate (PLP) measurements. Ages, heights, and ideal body weights of the two groups were similar as were reported energy, protein, and vitamin B-6 intakes obtained by using 24-h intake data collected on two nonconsecutive days separated by at least 1 wk. The reported vitamin B-6 intakes were 1.18 +/- 0.44 mg/d (means +/- SD). Plasma PLP levels in the obese and nonobese black women were similar; these levels were also similar to those observed previously for white obese and nonobese women having similar physical characteristics. All subjects had plasma PLP levels indicative of adequate status with one possible exception. Obesity did not affect the plasma PLP levels in these black women.

Plasma pyridoxal phosphate concentrations of men fed different levels of vitamin B-6

The vitamin B-6 status of 12 white, 3 black, and 7 men of other races was evaluated utilizing plasma pyridoxal phosphate concentrations after the males had been on controlled diets for 8 wk. The diets contained averages of 1.22-1.67 mg/d vitamin B-6 as calculated from food composition tables. The actual mean vitamin B-6 content of these diets as analyzed with Saccharomyces uvarum was 0.75-0.98 mg/d; the mean daily protein intakes were 80.8-84.5 g. All subjects had plasma pyridoxal phosphate concentrations (67.6-125.8 nmol/L) well within the normal range; the values of the different race and dietary groups were similar. Vitamin B-6 requirements were satisfied by the consumption of diets analyzed to contain means of 0.75-0.98 mg/d of the vitamin as demonstrated by plasma pyridoxal phosphate levels indicative of adequate status. Dietary vitamin B-6 intakes should be determined by actual analyses when requirements are being determined.

Effect of caloric restriction during pregnancy on maternal and fetal body composition in the obese Sprague-Dawley rat

The effects of 15, 30 or 50% caloric restriction during pregnancy on maternal and fetal compartments was determined in obese Sprague-Dawley rats. Pregnant and nonpregnant animals were assigned on a weight basis to one of the dietary treatments. All nutrients, except calories, were fed at levels to meet dietary requirements. Animals were killed on day 20 of treatment and fetuses were taken by Caesarian section. Pregnant animals achieved positive weight gain during 20 days of gestation at all levels of caloric restriction. Nonpregnant animals lost body weight when calories were restricted by 30 and 50%. Number of fetuses, fetal body nitrogen, and pup weight were not statistically different (P less than 0.05) among groups. Animals fed the 30 and 50% calorie-restricted diets showed a significant (P less than 0.05) decrease in total-body fat. Percent carcass protein tended to increase as dietary caloric restriction increased. The fetal compartment was apparently not affected by maternal caloric restriction up to 50% during pregnancy provided that all other nutrients were supplied in adequate amounts. Maternal stores were adversely affected at levels of 30 and 50% caloric restriction.

Effects of short-term aerobic conditioning and high cholesterol feeding on plasma total and lipoprotein cholesterol levels in sedentary young men

The plasma total cholesterol (TC) and lipoprotein cholesterol concentrations of sedentary young men (n = 23) were determined during 4 wk of controlled feeding and 6 wk of supervised aerobic conditioning. Subjects were assigned to dietary treatments of 400 mg cholesterol per day (M) or 1400 mg cholesterol per day (H); both diets had a P/S ratio of about 0.6. Dietary groups M and H were subdivided into exercise (MX and HX) and sedentary (MS and HS) groups. Compared to the sedentary groups, MX and HX exhibited significant (p less than 0.01) improvements in cardiorespiratory fitness. After 2 and 4 wk of high cholesterol feeding, group HS exhibited significant (p less than 0.05) elevations in TC (+30 +/- 7 and +32 +/- 9 mg/dl) with nonsignificant increases in very low-density lipoprotein cholesterol and low-density lipoprotein cholesterol. Group HX exhibited consistent weekly increases in high-density lipoprotein cholesterol (HDL-C) (from 46 +/- 3 mg/dl, the base level, to 53 +/- 4 mg/dl at wk 4) with aerobic conditioning. By combining exercise and sedentary group data at each level of dietary cholesterol it was shown that TC and HDL-C levels significantly (p less than 0.05) increased by the 4th wk of high cholesterol feeding. The TC/HDL-C ratio significantly (p less than 0.05) increased for the sedentary subjects as compared to all the exercising subjects by wk 4 of controlled feeding.

Carcass nitrogen as a predictor of protein requirement for mature female rats

The minimal level of dietary protein required for maintenance of nitrogen equilibrium was investigated using Sprague-Dawley rats, 12 months of age. Rats were fed casein, supplemented with methionine, at levels ranging from 0.84 to 5.18% of the diet for 4, 8 or 12 weeks and were compared to a control group fed a similar diet containing 9.90% protein or to a baseline group fed a stock diet. The effect of dietary protein levels on total serum protein and on liver and carcass composition was assessed. Protein requirement levels with 95% confidence intervals were predicted by linear regression. Dietary protein levels of 2.14% or lower were not adequate to maintain body weight and serum protein levels, and animals fed these diets had elevated levels of liver lipid. Protein nutriture of rats fed 3.20% protein was generally intermediate between those fed 2.14% or less and those fed 3.62% or greater. Compared to carcass nitrogen, carcass water was not as reliable a parameter for determination of protein requirements. Using the baseline group for comparison and carcass nitrogen as the dependent variable, a dietary protein requirement was predicted for these animals of 3.91--4.19% with confidence intervals of 3.50--4.56% and 3.13--5.48%, respectively. This level is comparable to the maintenance protein requirement of 4% indicated by the National Research Council for adult rats.