Seasonal variation in pH and alkalinity and recruitment of sunfish populations

• 1 In a study of five ponds sensitive to acid precipitation, we document seasonal acidification profiles and assess the impact of short-term acid pulses on the reproductive success of resident sunfish (Lepomis spp.).
• 2 Three years of water sampling at 2–3 week intervals showed substantial seasonal variation in pH and alkalinity consistent with a carbonate buffering system. Though all ponds shared a common seasonal pattern in pH, ponds with relatively low pH and alkalinity showed the greatest variation in these parameters. Spring minima may dispose some of the ponds towards episodes of extreme acidity during heavy spring rains.
• 3 Otolith analysis of young-of-the-year sunfish revealed recruitment failures for eggs laid early in spring in ponds with relatively low alkalinity and pH, and, in the most extreme case, missing day classes at subsequent irregular intervals even though average pH and alkalinity were well above those demonstrated to affect centrarchid fishes.
• 4 Age-class distributions of sunfishes revealed gaps in adult age distributions which could be traced through 3 years of the study, but there was no clear-cut relationship between pond acidification and the age structure of adult fish.
• 5 Seasonal profiles of acidity may enable researchers to predict the time during which a pond or lake may be highly sensitive to acid inputs. Comparative otolith analysis of young-of-the-year fishes and short-term continuous monitoring of water chemistry may provide an early warning of biological effects of acidification in sensitive bodies of water.

     

Plant virus infection development as affected by heavy metal stress

The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.     

Climate‐driven increases in storm frequency simplify kelp forest food webs

Climate models predict a dramatic increase in the annual frequency and severity of extreme weather events during the next century. Here we show that increases in the annual frequency of severe storms lead to a decrease in the diversity and complexity of food webs of giant kelp forests, one of the most productive habitats on Earth. We demonstrate this by linking natural variation in storms with measured changes in kelp forest food web structure in the Santa Barbara Channel using structural equation modeling (SEM). We then match predictions from statistical models to results from a multiyear kelp removal experiment designed to simulate frequent large storms. Both SEM models and experiments agree: if large storms remain at their current annual frequency (roughly one major kelp‐removing storm every 3.5 years), periodic storms help maintain the complexity of kelp forest food webs. However, if large storms increase in annual frequency and begin to occur year after year, kelp forest food webs become less diverse and complex as species go locally extinct. The loss of complexity occurs primarily due to decreases in the diversity and complexity of higher trophic levels. Our findings demonstrate that shifts in climate‐driven disturbances that affect foundation species are likely to have impacts that cascade through entire ecosystems.     

Genome‐enabled development of DNA markers for ecology,evolution and conservation

Molecular markers have become a fundamental piece of modern biology’s toolkit. In the last decade, new genomic resources from model organisms and advances in DNA sequencing technology have altered the way that these tools are developed, alleviating the marker limitation that researchers previously faced and opening new areas of research for studies of non‐model organisms. This availability of markers is directly responsible for advances in several areas of research, including fine‐scaled estimation of population structure and demography, the inference of species phylogenies, and the examination of detailed selective pressures in non‐model organisms. This review summarizes methods for the development of large numbers of DNA markers in non‐model organisms, the challenges encountered when utilizing different methods, and new research applications resulting from these advances.     

STREAK—A VIRUS DISEASE OF TOMATOES

A comparison of streak disease of tomatoes, derived from commercial glasshouses, and experimental streak produced by combined inoculation of the viruses of potato mosaic and tobacco mosaic, is given in detail.
The characters employed in comparison are the host range of each virus and its resistance to various temperatures, to different concentrations of alcohol, and to ageing in vitro .
Glasshouse streak and tobacco mosaic show an equal resistance to alcohol, heat and ageing in vitro , and have, in addition, an identical host range. Treatment for 1 hour with 90 per cent, alcohol and for 10 minutes at 85⁰ C. did not destroy the infectivity of either of these viruses.
Glasshouse streak is shown not to contain the virus of potato mosaic, but is of itself able to produce necrosis in tomatoes without the participation of potato mosaic. The factors underlying this have not been determined.
It is concluded that tobacco mosaic and the mosaic of glasshouse streak are probably identical, and that much of the streak occurring in glasshouses is due to a single virus, and not a mixed infection of this with potato mosaic.