The Salinas River sampling site has been used as a least-impacted reference site in previous toxicity studies and is generally classified as non-toxic, based on acute exposure studies. This increase in potency after a rain event is consistent with an influx of pesticides, and the chemical analyses show higher levels of several pesticides of concern in November at all three sites . Climate change is altering rainfall patterns in many areas of the world and understanding how these changes may impact sensitive aquatic systems is crucial for monitoring water quality. Surface water exposure caused significant changes in D. magna swimming behavior both before and after a first flush event, even at low concentrations. In September, prior tofirst flush, we detected strong dose-response patterns in total distance moved and log-linear dose response in photomotor response. Daphnia magna exposed to all concentrations of surface water in September increased their movement in response to light stimulus, while control groups reduced their activity. This may have implications for survival in natural populations. Individuals who cannot respond to predator cues, or that show impaired and/or altered responses, may have an increased risk of predation. It is important to note that changes in swimming behavior in organisms exposed to water samples from Alisal Creek in September may have been partially capturing a lethal response. This treatment group had significant mortality in all exposure concentrations , so it is possible these individuals were exhibiting not only sublethal,planting blueberries in pots but also delayed lethal toxic responses. Future studies should consider including recovery periods in their experimental design and analyses to parse out whether behavioral impacts are reversable, indicative of long-term effects, or even subsequent mortality.
Due to the high mortality observed for Quail Creek in September, we were unable to make any behavioral comparisons. It is notable that the level of methomyl detected at this site was greater than three times the EPA chronic fish exposure level, and it is likely that methomyl represents a main driver of the toxicity for this site. It is possible that additional contaminants are present at this site, which were not included in our analysis. Many pharmaceuticals are known to cause hyperactivity and have been detected in wastewater at other sites in California. Taken together, these findings illustrate the importance of conducting sublethal assessments to link physiological responses to chemical monitoring data. After the first flush , we measured hypoactivity for all sites during at least one light condition, in at least one concentration. Many of the pesticides we detected in surface water samples are known to reduce the swimming speed and distance of D. magna at concentrations relevant to those detected in our samples. We detected changes to the photomotor responses of D. magna exposed to low concentrations of surface water from all three sites when compared with controls, demonstrating biologically relevant impacts. Despite low mortality observed in the Salinas River site during both testing dates, we detected altered behavior even at the highest dilution of 6% ambient water in November. Hypoactivity and altered photomotor responses may reduce the capacity of D. magna to follow normal behaviors, such as patterns of diel vertical migration and horizontal distribution, thus increasing predation risk and reducing overall fitness. We measured significant changes in the swimming behavior of D. magna after acute exposures to CHL and IMI in single and binary chemical exposures, and as components of agricultural surface waters both before and after a first flush event.
Surface waters contained complex mixtures including CHL and IMI, but also other pesticides of concern including neonicotinoids, pyrethroids, carbamates, and organophosphates. We determined that swimming behaviors of D. magna are sensitive endpoints for the sublethal assessments of the tested pesticides, and for surface water exposures. We detected chemical-specific changes in D. magna swimming behavior for both CHL and IMI exposures. Imidacloprid exposure at environmentally relevant concentrations caused hypoactivity for both concentrations tested, across both dark and light conditions, following a dose-response pattern. The increase in activity over the light period represents a return to baseline following a change in light conditions. Our results are consistent with previous findings: IMI negatively impacts nerve conduction and alters swimming behavior in D. magna and is known to inhibit acetylcholinesterase . Past research has shown AChE inhibition is linked to changes in swimming response, and that a 50% decrease in AChE activity can cause enough change in swimming behavior in D. magna to be described as toxic . In a recent study examining the effects of IMI on the amphipod Gammarus fossarum, IMI stimulated locomotor activity at low exposure concentrations and inhibited activity at higher concentrations . Daphnia magna are particularly tolerant to neonicotinoids, illustrating the potential for impacts in other more sensitive organisms known to inhabit IMI-polluted waterways. We detected significant hypoactivity in individuals exposed to CHL under dark conditions. This is consistent with previous studies on D. magna demonstrating that CHL is a known neurotoxicant for this species, causing changes in muscle contraction via interaction with the ryanodine receptor. Low levels of CHL exposure have been shown to produce dose-dependent inhibition of swimming, and decreased responses to light stimulation in a recent study. Another recent study examining effects of single chemical exposure to CHL and IMI, among other chemicals, at low concentrations had effects on total distance moved of D. magna.
We observed hypoactivity under dark conditions and hyperactivity under light conditions for D. magna after exposure to binary mixtures of CHL and IMI. Hyperactivity could suggest a possible disruption of signal transmission in the vision or nervous systems and has been observed for IMI exposures at low exposure levels in other studies. The hyperactivity observed in the low IMI exposure group was notable in that the response was inverse from both single chemical exposures performed at the same concentrations, potentially indicative of an antagonistic response. Our finding is partially consistent with Hussain et al.; however, where investigators also found hyperactivity under light conditions but no significance under dark conditions. It is relevant to note that our experimental design differed from that of Hussain et al. , who used one exposure vessel containing 50 Daphnids per treatment group, whereas we used fewer Daphnia per exposure vessel, with six exposure vessels per treatment. For future studies, increased replication could improve the ability to determine whether small changes in total distance moved could also be significant. Considering the significance of our other treatments and endpoints, and that our replication exceeded many previously published studies, we propose that our experimental design was sufficient to detect many sublethal effects . Sublethal impacts can result in ecologically relevant effects on individual fitness, populations, and communities. In pesticide-contaminated aquatic environments, overall invertebrate biomass and diversity are reduced as sensitive individuals and species decline . With the increasing number of pesticides being detected in waterways worldwide,blackberries in containers rapid and standardized testing approaches are urgently needed. For many species and chemicals of interest, biochemical reactions can visually manifest via behavioral changes, making behavior a highly integrative and informative endpoint for exposure. Meta-analysis of behavior in comparison to other toxicological endpoints such as development, lethality, and reproduction, showed that behavioral analyses are advantageous to assess the effects of environmental chemicals due to their relative speed and sensitivity. Behavioral assays possess great potential as rapid, high throughput monitoring tools. The world now seems prepared to seriously consider agricultural trade liberalization and domestic food and farm policy reform. The economic summits of the major western countries, the Organization for Economic Cooperation and Development , the World Bank, the International MOnetary Fund, the General Agreement on Tariffs and Trade , and numerous other international agencies now recognize the necessity of multilateral and phased liberalization. In other words, a dramatic reduction in protection for agriculture throughout the world would appear to be the right answer. Simple economic analysis has demonstrated that, in a world in which pure competition maximizes net economic payoff, the deadweight losses resulting from current policy interventions in food and agriculture are enormous.
Unfortunately, we do not live in such a world: Only second-best outcomes are possible, governments do not maximize social welfare, pure non–distortionary–that is, decoupled– transfers do not exist, political and economic markets are not separable, and policies for other sectors–especially general macroeconomic policies–are not perfectly designed and implemented. Simply put, there are many complications in evaluating agricultural and food policy reform. This paper will examine one in particular–the macroeconomic risk nations face in the implementation of food and agricultural policy reform. In all of the recent studies of agricultural trade liberalization and agricultural policy reform, little if any attention has been paid to the macroeconomic environment that might exist during the implementation phase of various proposals. This is indeed surprising because the origins of many farm policies can be traced directly to the macroeconomic environment. Moreover~ the dynamic adjustment paths that would evolve following the implementation of particular reform proposals would be heavily dependent upon macroeconomic conditions~ such as the level of real interest rates and exchange rates~ the nature of monetary and fiscal policies–whether expansionary or deflationary– and so on. This paper focuses on four major themes. First~ macroeconomic and international linkages are significant and must be recognized in any framework for policy design and reform. Second~ the intercountry linkages of both agricultural and macroeconomic policies are especially important for less-developed countries . Third~ political economic markets for policy reform exist and governments throughout the world have an opportunity to supply reform through the reduction of transaction costs. Transaction costs can be reduced through alternative compensation schemes which are motivated by behavioral analysis of political economic markets. And fourth, macroeconomic and international linkages are a major component in the design of flexible agricultural policies that can respond to changing conditions. These themes·are used to examine agricultural policy reform and trade liberalization in the current environment.Throughout much of the developed world~ macro policies in the two decades following World War II afforded a unique period of macroeconomic stability. As a result~ concern regarding the macroeconomic linkages with food and agricultural systems largely disappeared. In the early 1970s with the major changes in monetary polices and central bank behavior, macroeconomic linkages were once again recognized as prime factors complicating agriculture and food policy. The roller coaster ride that agriculture has experienced over the last two decades has been significantly influenced by macro and international linkages . Recent history stands in sharp contrast to the basic stability of the 1950s and 1960s. This roller coaster is not unprecedented. For example, the period 1900 through 1915 is surprisingly similar to the 1970s, and the late 1920s through 1930s have some of the same characteristics of the 1980s. A longer historical perspective demonstrates that macroeconomic disturbances and their links to agricultural sectors throughout the world were central to the emergence of direct governmental intervention in food and agricultural systems. For example, in the case of OECO countries, there have been abrupt increases in governmental intervention during periods of macroeconomic contractions accompanying downward movements in agricultural prices. The first major wave of increasing intervention.in agriculture occurred during the last quarter of the 19th Century, following several decades of trade liberalization. Prior to this, agricultural trade had expanded dramatically due to the removal of tariffs and import quotas and to the increasing availability of low price grain from the United States and Europe. The protectionism following this trade expansionary period was motivated by what was then referred to as Europe’s great depression.Policy responses varied across countries. England alone maintained a staunch free trade position while Germany, France, and Italy restored agricultural tariffs from the mid-1880s onward. In Denmark and the Netherlands, falling grain prices encouraged the expansion of livestock activities. In the the United States, despite expanding grain exports, farmers did not ignore depressed prices. The period from 1873 to 1896 witnessed increasing levels of farmer mobilization through the Grange and populace movements. Farmer demands were wide ranging, but a major objective was a change in banking policy to promote inflationary expansion of money supplies. Lobbying efforts to this end continued into the Twentieth Century and were partially responsible for the institutional changes that created the Federal Reserve in 1913 and the federal land banks in 1916. The U. S. government’s massive intervention in agriculture in the 1930s followed a farm crisis that had its origins in the macroeconomic adjustments after World War I.