The hypothesis that the morphometric characteristics of the littoral zone of lakes are a major determinant of submerged macrophyte biomass was tested in Lake Memphremagog (Québec‐Vermont) by studying the relationship between maximum biomass of submerged macrophytes and physical and sediment characteristics of the littoral zone. The slope of the littoral zone accounted for 72% of the observed variability in maximum submerged macrophyte biomass (MSMB). By also incorporating sediment organic matter the variance explained was raised to 88% ( P < 0.0001). A model based on only slope as predictor of MSMB was improved by considering slopes ≷5.33%: urn:x-wiley:00243590:media:lno19863151072:lno19863151072-math-0001 The power of these two equations to predict the MSMB in a variety of temperate lakes was high ( r = 0.90, P < 0.0001). However, the temperate zone model overestimates the MSMB in highly turbid lakes where irradiance rather than slope is pre‐eminent and underestimates the biomass in semitropical and tropical lakes.
The seasonality of phytoplankton cell lysis rates in the NW Mediterranean coastal waters was examined based on measurements of the dissolved esterase activity between 1995 and 1998 in the Blanes Bay (NE Spain). The temporal variability of phytoplankton biomass and gross primary production (GPP) were characterized by a late winter bloom dominated by diatoms and high GPP in summer despite the low phytoplankton biomass in this season. The phytoplankton lysis rates were found to be strongly seasonal, being highest in summer (mean ± SE = 0.41 ± 0.049 d −1 ) when values as high as 1.47 d −1 were attained. However, during the rest of the year, phytoplankton lysis rates remained low, particularly in winter (0.061 ± 0.005 d −1 ). There was a strong ( R 2 = 0.71, P < 0.00001) positive relationship between monthly average lysis rates and water temperature. In addition, monthly average lysis rates followed gross primary production with a maximum correlation ( r = 0.65, P < 0.05) at a lag time of 1–2 months, similar to the time span from bloom initiation to bloom collapse. These results identify phytoplankton cell lysis as an important route of phytoplankton carbon flow in Blanes Bay.
Abstract Although clonal species are dominant in many habitats, from unicellular organisms to plants and animals, ecological and particularly evolutionary studies on clonal species have been strongly limited by the difficulty in assessing the number, size and longevity of genetic individuals within a population. The development of molecular markers has allowed progress in this area, and although allozymes remain of limited use due to their typically low level of polymorphism, more polymorphic markers have been discovered during the last decades, supplying powerful tools to overcome the problem of clonality assessment. However, population genetics studies on clonal organisms lack a standardized framework to assess clonality, and to adapt conventional data analyses to account for the potential bias due to the possible replication of the same individuals in the sampling. Moreover, existing studies used a variety of indices to describe clonal diversity and structure such that comparison among studies is difficult at best. We emphasize the need for standardizing studies on clonal organisms, and particularly on clonal plants, in order to clarify the way clonality is taken into account in sampling designs and data analysis, and to allow further comparison of results reported in distinct studies. In order to provide a first step towards a standardized framework to address clonality in population studies, we review, on the basis of a thorough revision of the literature on population structure of clonal plants and of a complementary revision on other clonal organisms, the indices and statistics used so far to estimate genotypic or clonal diversity and to describe clonal structure in plants. We examine their advantages and weaknesses as well as various conceptual issues associated with statistical analyses of population genetics data on clonal organisms. We do so by testing them on results from simulations, as well as on two empirical data sets of microsatellites of the seagrasses Posidonia oceanica and Cymodocea nodosa . Finally, we also propose a selection of new indices and methods to estimate clonal diversity and describe clonal structure in a way that should facilitate comparison between future studies on clonal plants, most of which may be of interest for clonal organisms in general.
Abstract. The relationship between the partial pressure of carbon dioxide (pCO2) and dissolved organic carbon (DOC) concentration in Brazilian lakes, encompassing 225 samples across a wide latitudinal range in the tropics, was tested. Unlike the positive relationship reported for lake waters, which was largely based on temperate lakes, we found no significant relationship for low-latitude lakes (< 33°), despite very broad ranges in both pCO2 and DOC levels. These results suggest substantial differences in the carbon cycling of low-latitude lakes, which must be considered when upscaling limnetic carbon cycling to global scales.
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 171:97-108 (1998) - doi:10.3354/meps171097 Root production and belowground seagrass biomass Carlos M. Duarte1,*, Martín Merino2, Nona S. R. Agawin3, Janet Uri3, Miguel D. Fortes3, Margarita E. Gallegos4, Nùria Marbá5, Marten A. Hemminga5 1Centro de Estudios Avanzados de Blanes, CSIC, Camí de Santa Bárbara s/n, E-17300 Blanes, Girona, Spain 2Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, 04510 México D.F., México 3Marine Science Institute, CS, University of The Philippines, Diliman, Quezon City, The Philippines 4Departamento de Hidrobiología, Universidad Autónoma Metropolitana - Iztapalapa, Michoacán y Purísima, Col. Vicentina, AP 55-535, 09340 México D.F., México 5Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Vierstraat 28, 4401 EA Yerseke, The Netherlands *E-mail: duarte@ceab.csic.es ABSTRACT: The root and rhizome biomass of the seagrass species present in 3 mixed and 2 monospecific meadows representative of different floras (Spanish Mediterranean, Mexican Caribbean, Kenyan coast, and the South China Sea off The Philippines) was examined to test for the existence of general patterns in the distribution of their biomass in the sediments, and to test a simple approach based on age determinations to estimate root production. The thickness of the roots was scaled to the thickness of the seagrass rhizomes (r = 0.92, p < 0.001). Root and rhizome biomass were high (>100 and >200 g DW m-2, respectively) for the mixed meadows examined; these belowground structures had a projected surface area often exceeding 1 m2 m-2 when roots and rhizomes were considered together, and they formed a dense web of root material comprising several hundred meters per square meter. Belowground biomass showed considerable vertical stratification within the sediments, with a tendency for the larger species to extend deeper into the sediments than smaller ones. This tendency for segregation should reduce the potential interspecific competition for sediment resources, which is likely to be greater in the uppermost layers, where the belowground biomass is more evenly distributed among species. The rate of adventitious root production on vertical shoots varied from species that produced a root on almost every node to species that produced 1 adventitious root for every 10 nodes. Root production--both on horizontal rhizomes and vertical shoots--was substantial, with the combined root production approaching, or exceeding, 1000 g DW m-2 yr-1. The resulting root turnover was quite high, with most values ranging between 2 and 10 yr-1, indicative of a characteristic turnover time of months for the root compartment. The estimates of root production derived here often exceed those of rhizome production and reach values comparable to leaf production, clearly demonstrating that root production is an important component (up to 50%) of total seagrass production. KEY WORDS: Seagrass · Roots · Rhizomes · Biomass · Production Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 171. Publication date: October 01, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.
We depend on the sea, economically, social well-being and for the quality of our lives. Yet, direct and indirect human activities have affected the marine environment causing many problems, such as overfishing and pollution at the local scale and ocean warming and acidification at the global one. Hence, addressing the cumulative effects of these activities is required to conserve the marine environment for our current and future generations. Social commitment and support for these actions depends, however, on awareness, and requires, therefore, understand citizen's awareness and perceptions on these issues. We assessed the awareness and perceptions of Saudi citizens on ocean issues through an online questionnaire about environmental issues globally and in the country. The survey was completed by 1,524 Saudi citizens eighteen-year-old and above, with different geographic distributions, gender and educational status. Participants identified climate change within the top three global problems, with variable level of information and trust on different sources of environmental information. Pollution, specifically littering, sewage pollution and oil pollution were identified as the top three major marine issues in Saudi Arabia, with respondents demanding immediate action through imposing fines to polluters and more regulatory constraints to activities that act as sources of pollution, as well as supporting research in science and technologies to address these environmental issues.
