Farm soils, their management and fertilization.

Mode of access: Internet.

The determination of dominance and the modification of behavior in alternative (Mendelian) inheritance, by conditions surrounding or incident upon the germ cells at fertilization.

"Correction and addendum."

Pasture productivity of crested wheatgrass as influenced by nitrogen fertilization and alfalfa

Prepared in cooperation with Dept. of Animal Science, North Dakota Agricultural Experiment Station.

Effects of weed control and fertilization on botanical composition and forage yields of Kentucky bluegrass pasture

Bibliography: p. 27-28.

Fertilization of branching Acropora

Acropora is one of the largest taxonomic groups of scleractinian corals in the Indo-Pacific and contributes towards the establishment of coral communities in the Ryukyu Islands. Branching Acropora populations have a component of asexual reproduction; however, this may lead to a decline in genetic diversity, leaving populations vulnerable to environmental changes. Therefore, a sufficient supply of larvae produced via sexual reproduction is necessary to maintain genetic diversity in the branching Acropora communities. Fertilization success in branching Acropora depends on a variety of factors, including genetic and environmental conditions. How genotype and/or genetic compatibility drives fertilization rates in Acropora communities under natural conditions has not been investigated. To investigate how genotype and/or genetic compatibility determine fertilization rates in Acropora communities over the long-term, cross-mating experiments with branching Acropora using the same colonies were conducted from 2006 to 2011 in an aquarium. Acropora from cultured and natural colonies collected from a reef (26° 40' 19.2'' N, 127° 52' 40.8'' E) were used. Fertilization rates showed less variation within the same crossing combinations, but large variation across years for the same genotypes of focal colonies. Results indicated that fertilization rate was highly variable depending on genotype compatibility with different mating partners. Additionally, simulations of fertilization rates with increasing population size revealed that small populations that had low genetic diversity (fewer than 10 genotypes) failed to fertilize. These results support the establishment or maintenance of source populations that facilitate sufficient genetic diversity of branching Acropora to enhance coral community restoration.

Reliably estimating the effect of toxicants on fertilization success in marine broadcast spawners

Recently, there has been a dramatic increase in the number of ecotoxicological studies examining the effects of toxicants on fertilization success in marine broadcast spawners and it appears that this life-history stage is one of the most vulnerable to toxicants. Most of the studies examining this issue use single sperm concentrations in their assays. Here, I discuss recent advances in fertilization ecology that suggest this technique has some severe limitations resulting in unreliable estimations of the size and direction of toxicant effects. I present an alternative assay technique and two metrics (F-max and [Sperm](max)) that will reliably estimate the size of a toxicant's effect on fertilization success. This technique has the added advantage of making comparisons among species and studies easier without an impractical increase in effort. (c) 2006 Elsevier Ltd. All rights reserved.

The effects of fertilization and simulated grazing on the community structure of a seagrass bed in South Florida

The importance of resource supply and herbivory in driving competitive interactions among species has been an important but contentious issue within ecology. These variables exhibit different effects on species competition when manipulated in isolation but interact when manipulated together. I tested the direct and interactive effects of nutrient addition and simulated grazing (clipping) on the competitive performance of primary producers and community structure of a seagrass bed in South Florida. One square meter experimental plots were established in a mixed seagrass meadow from August 2007 to July 2009. The experiment was a 3 x 3 factorial experiment: 3 fertility treatments: control, medium (2.4 mg N d−1 and 80 µg P day −1) and high (4.8 mg N d−1 and 160 µg P day−1) x 3 clipping intensities (0, 25% and 50 % biomass removal (G)) x 5 replicates for each treatment = 45 plots). Nutrient additions and simulated grazing were done every two months. Fertilization and simulated grazing decreased sexual reproduction in S. filiforme. Fertilization increased competitive dominance within the primary producers while simulated grazing counteracted this effect by removal of the dominant species. Fertilization ameliorated the negative impacts of simulated grazing while simulated grazing prevented competitive exclusion in the fertilized plots. Nutrient addition and simulated grazing both exerted strong control on plant performance and community structure. Neither bottom up nor top down influences was eliminated in treatments where both factors where present. The effects of fertilization on plant performance were marked under all clipping intensities indicating that the system is regulated by nutrient availability both in the presence or absence of grazers. Clipping effects were strong under both fertilized and unfertilized conditions indicating that the seagrass bed can be simultaneously under top-down control by grazers.

Responses of seagrass communities to fertilization along a gradient of relative availability of nitrogen and phosphorus in a carbonate environment

Patterns of relative nutrient availability in south Florida suggest spatial differences regarding the importance of nitrogen (N) and phosphorus (P) to benthic primary producers. We did a 14-month in situ fertilization experiment to test predictions of N and P limitation in the subtropical nearshore marine waters of the upper Florida Keys. Six sites were divided into two groups (nearshore, offshore) representing the endpoints of an N: P stoichiometric gradient. Twenty-four plots were established at each site with six replicates of each treatment (1N, 1P, 1N1P, control), for a total of 144 experimental plots. The responses of benthic communities to N and P enrichment varied appreciably between nearshore and offshore habitats. Offshore seagrass beds were strongly limited by nitrogen, and nearshore beds were affected by nitrogen and phosphorus. Nutrient addition at offshore sites increased the length and aboveground standing crop of the two seagrasses, Thalassia testudinum and Syringodium filiforme, and growth rates of T. testudinum. Nutrient addition at nearshore sites increased the relative abundance of macroalgae, epiphytes, and sediment microalgae. N limitation of seagrass in this carbonate system was clearly demonstrated. However, added phosphorus was retained in the system more effectively than N, suggesting that phosphorus might have important long-term effects on these benthic communities. The observed species-specific responses to nutrient enrichment underscores the need to monitor all primary producers when addressing questions of nutrient limitation and eutrophication in seagrass communities.

Ecosystem Structure and Function Still Altered Two Decades After Short-Term Fertilization of a Seagrass Meadow

An oligotrophic phosphorus (P) limited seagrass ecosystem in Florida Bay was experimentally fertilized in a unique way. Perches were installed to encourage seabirds to roost and deliver an external source of nutrients via defecation. Two treatments were examined: (1) a chronic 23-year fertilization and (2) an earlier 28-month fertilization that was discontinued when the chronic treatment was initiated. Because of the low mobility of P in carbonate sediments, we hypothesized long-term changes to ecosystem structure and function in both treatments. Structural changes in the chronic treatment included a shift in the dominant seagrass species from Thalassia testudinum to Halodule wrightii, large increases in epiphytic biomass and sediment chlorophyll-a, and a decline in species richness. Functional changes included increased benthic metabolism and quantum efficiency. Initial changes in the 28-month fertilization were similar, but after 23 years of nutrient depuration T. testudinum has reestablished itself as the dominant species. However, P remains elevated in the sediment and H. wrightii has maintained a presence. Functionally the discontinued treatment remains altered. Biomass exceeds that in the chronic treatment and indices of productivity, elevated relative to control, are not different from the chronic fertilization. Cessation of nutrient loading has resulted in a superficial return to the pre-disturbance character of the community, but due to the nature of P cycles functional changes persist.

The effects of carbon dioxide fertilization on the ecology of tropical seagrass communities

Increasing atmospheric CO2 concentrations associated with climate change will likely influence a wide variety of ecosystems. Terrestrial research has examined the effects of increasing CO2 concentrations on the functionality of plant systems; with studies ranging in scale from the short-term responses of individual leaves, to long-term ecological responses of complete forests. While terrestrial plants have received much attention, studies on the responses of marine plants (seagrasses) to increased CO 2(aq) concentrations remain relatively sparse, with most research limited to small-scale, ex situ experimentation. Furthermore, few studies have attempted to address similarities between terrestrial and seagrass responses to increases in CO2(aq). The goals of this dissertation are to expand the scope of marine climate change research, and examine how the tropical seagrass, Thalassia testudinum responds to increasing CO 2(aq)concentrations over multiple spatial and temporal scales. ^ Manipulative laboratory and field experimentation reveal that, similar to terrestrial plants, seagrasses strongly respond to increases in CO 2(aq) concentrations. Using a novel field technique, in situ field manipulations show that over short time scales, seagrasses respond to elevated CO2(aq) by increasing leaf photosynthetic rates and the production of soluble carbohydrates. Declines in leaf nutrient (nitrogen and phosphorus) content were additionally detected, paralleling responses from terrestrial systems. Over long time scales, seagrasses increase total above- and belowground biomass with elevated CO2(aq), suggesting that, similar to terrestrial research, pervasive increases in atmospheric and oceanic CO2(aq) concentrations stand to influence the productivity and functionality of these systems. Furthermore, field experiments reveal that seagrass epiphytes, which comprise an important component of seagrass ecosystems, additionally respond to increased CO2(aq) with strong declines in calcified taxa and increases in fleshy taxa. ^ Together, this work demonstrates that increasing CO2(aq) concentrations will alter the functionality of seagrass ecosystems by increasing plant productivity and shifting the composition of the epiphyte community. These results have implications for future rates of carbon storage and sediment production within these widely distributed systems.^

Left to right: Sharon Ewe and Calvin Liu applying Florida Bay sediments to dwarf mangrove forest as part of a fertilization experiment, Taylor Slough

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. This image is made available for non-commercial or educational use only.

Left to right: Sharon Ewe and Calvin Liu applying Florida Bay sediments to dwarf mangrove forest as part of a fertilization experiment, Taylor Slough

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. This image is made available for non-commercial or educational use only.

Seawater carbonate chemistry and sperm swimming speed, fertilization success of the Australasian sea urchin Heliocidaris erythrogramma in lab experiment

Background: Climate change will lead to intense selection on many organisms, particularly during susceptible early life stages. To date, most studies on the likely biotic effects of climate change have focused on the mean responses of pooled groups of animals. Consequently, the extent to which inter-individual variation mediates different selection responses has not been tested. Investigating this variation is important, since some individuals may be preadapted to future climate scenarios. Methodology/Principal Findings: We examined the effect of CO2-induced pH changes ("ocean acidification") in sperm swimming behaviour on the fertilization success of the Australasian sea urchin Heliocidaris erythrogramma, focusing on the responses of separate individuals and pairs. Acidification significantly decreased the proportion of motile sperm but had no effect on sperm swimming speed. Subsequent fertilization experiments showed strong inter-individual variation in responses to ocean acidification, ranging from a 44% decrease to a 14% increase in fertilization success. This was partly explained by the significant relationship between decreases in percent sperm motility and fertilization success at delta pH = 0.3, but not at delta pH = 0.5. Conclusions and Significance: The effects of ocean acidification on reproductive success varied markedly between individuals. Our results suggest that some individuals will exhibit enhanced fertilization success in acidified oceans, supporting the concept of 'winners' and 'losers' of climate change at an individual level. If these differences are heritable it is likely that ocean acidification will lead to selection against susceptible phenotypes as well as to rapid fixation of alleles that allow reproduction under more acidic conditions. This selection may ameliorate the biotic effects of climate change if taxa have sufficient extant genetic variation upon which selection can act.