A new approach for estimating northern peatland gross primary productivity using a satellite-sensor-derived chlorophyll index

Carbon flux models that are largely driven by remotely sensed data can be used to estimate gross primary productivity (GPP) over large areas, but despite the importance of peatland ecosystems in the global carbon cycle, relatively little attention has been given to determining their success in these ecosystems. This paper is the first to explore the potential of chlorophyll-based vegetation index models for estimating peatland GPP from satellite data. Using several years of carbon flux data from contrasting peatlands, we explored the relationships between the MERIS terrestrial chlorophyll index (MTCI) and GPP, and determined whether the inclusion of environmental variables such as PAR and temperature, thought to be important determinants of peatland carbon flux, improved upon direct relationships. To place our results in context, we compared the newly developed GPP models with the MODIS (Moderate Resolution Imaging Spectrometer) GPP product. Our results show that simple MTCI-based models can be used for estimates of interannual and intra-annual variability in peatland GPP. The MTCI is a good indicator of GPP and compares favorably with more complex products derived from the MODIS sensor on a site-specific basis. The incorporation of MTCI into a light use efficiency type model, by means of partitioning the fraction of photosynthetic material within a plant canopy, shows most promise for peatland GPP estimation, outperforming all other models. Our results demonstrate that satellite data specifically related to vegetation chlorophyll content may ultimately facilitate improved quantification of peatland carbon flux dynamics

Using MODIS derived <i>f</i>PAR with ground based flux tower measurements to derive the light use efficiency for two Canadian peatlands

International audienceWe used satellite remote sensing data; fraction of photosynthetically active radiation absorbed by vegetation (fPAR) from the Moderate Resolution Imaging Spectroradiometer (MODIS) in combination with tower eddy covariance and meteorological measurements to characterise the light use efficiency parameter (?) variability and the maximum ? (?max) for two contrasting Canadian peatlands. Eight-day MODIS fPAR data were acquired for the Mer Bleue (2000 to 2003) and Western Peatland (2004). Flux tower eddy covariance and meteorological measurements were integrated to the same eight-day time stamps as the MODIS fPAR data. A light use efficiency model: GPP=? * APAR (where GPP is Gross Primary Productivity and APAR is absorbed photosynthetically active radiation) was used to calculated ?. The ?max value for each year (2000 to 2003) at the Mer Bleue bog ranged from 0.58 g C MJ?1 to 0.78 g C MJ?1 and was 0.91 g C MJ?1 in 2004, for the Western Peatland. The average growing season ? for the Mer Bleue bog for the four year period was 0.35 g C MJ?1 and for the Western Peatland in 2004 was 0.57 g C MJ?1. The average snow free period ? for the Mer Bleue bog over the four year period was 0.27 g C MJ?1 and for the Western Peatland in 2004 was 0.39 g C MJ?1. Using the light use efficiency method we calculated the ?max and the annual variability in ? for two Canadian peatlands. We determined that temperature was a growth-limiting factor at both sites Vapour Pressure Deficit (VPD) however was not. MODIS fPAR is a useful tool for the characterization of ? at flux tower sites

Modeling seasonal to annual carbon balance of Mer Bleue Bog, Ontario, Canada

Northern peatlands contain enormous quantities of organic carbon within a few meters of the atmosphere and play a significant role in the planetary carbon balance. We have developed a new, process-oriented model of the contemporary carbon balance of northern peatlands, the Peatland Carbon Simulator (PCARS). Components of PCARS are (1) vascular and nonvascular plant photosynthesis and respiration, net aboveground and belowground production, and litterfall; (2) aerobic and anaerobic decomposition of peat; (3) production, oxidation, and emission of methane; and (4) dissolved organic carbon loss with drainage water. PCARS has an hourly time step and requires air and soil temperatures, incoming radiation, water table depth, and horizontal drainage as drivers. Simulations predict a complete peatland C balance for one season to several years. A 3-year simulation was conducted for Mer Bleue Bog, near Ottawa, Ontario, and results were compared with multiyear eddy covariance tower CO2 flux and ancillary measurements from the site. Seasonal patterns and the general magnitude of net ecosystem exchange of CO2 were similar for PCARS and the tower data, though PCARS was generally biased toward net ecosystem respiration (i.e., carbon loss). Gross photosynthesis rates (calculated directly in PCARS, empirically inferred from tower data) were in good accord, so the discrepancy between model and measurement was likely related to autotrophic and/or heterotrophic respiration. Modeled and measured methane emission rates were quite low. PCARS has been designed to link with the Canadian Land Surface Scheme (CLASS) land surface model and a global climate model (GCM) to examine climate-peatland carbon feedbacks at regional scales in future analyses

Resource management: European viewpoints

The Marine Environment and Resource Management - Should careful and rational management of fish stocks be considered a myth or a realistic prospect? Recent history has shown how. because of over-exploitation of certain fish-stocks - among which herring. Anchovy and cod are prime examples - the survival of some species has become an acute problem. Today all fishing zones are threatened, and no stock is safe from potential collapse. The situation is so serious that some scientists and fish- workers' organisations have acted to sound the alarm and to demand from governments that measures to protect the resource be implemented. However, looking beyond the indispensable need for legislation, it is the search for maximum profit which, unfortunately, so often governs fish production and marketing that must be challenged. Moreover, the question of resource management must integrate the need to safe-guard the ecology of the marine environment, which requires profound changes of mentality. In Lisbon, Portugal, in June 1989, about one hundred scientists, fishermen and organization representatives from 25 different countries met at a symposium to develop their thinking on these questions. In this dossier, we publish some papers by European speakers at this inter-national meeting organised by ICSF. (56pp.) (Bellec, F. (ed)

Systematics and distributions of the genera Cyrtusa Erichson, Ecarinosphaerula Hatch, Isoplastus Horn, Liocyrtusa Daffner, Lionothus Brown, and Zeadolopus Broun of the United States and Canada (Coleoptera: Leiodidae: Leiodinae: Leiodini)

The following genera of Leiodini (Coleoptera: Leiodidae: Leiodinae) of the continental United States and Canada are reviewed: Cyrtusa Erichson, with two species; Isoplastus Horn, with two species (one new); Liocyrtusa Daffner, with three species; Lionothus Brown, with five species (three new), and Zeadolopus Broun, with four species (all genera are in the “Cyrtusa genus group”) and Ecarinosphaerula Hatch, with one named species (in the “Leiodes genus group”). The new species are Isoplastus floridanus Peck and Cook of Florida; Lionothus bidentatus Peck and Cook of Texas and Oklahoma, Lionothus exiguus Peck and Cook of Florida and Texas, and Lionothus parvoculus Peck and Cook of Arizona and New Mexico. Bionomic data on the species are given, and complete known distributions are mapped

La consolidation de l’Europe bleue : nouveau contexte international et nouveaux enjeux

Each of the member states of the European Economic Community (EEC) has extended, through a common agreement, its own fishing grounds to 200 miles, thus leading to the creation, since 1977, of the Community waters whose exploitation would be subjected to the common fisheries policy of the EEC. The widespread extension of fishing grounds throughout Europe together with the state of overfishing in the North-East Atlantic have led the EEC to elaborate a policy in order to protect the interests of its member states, to make their fishing vessels competitive, and to ensure the stability of the fishing industry. This paper looks into the implementation of the fisheries policy of the EEC, internally — namely access s rights to Community waters, the coordination of markets and producers, aid to modernize the vessels - as well as regarding foreign countries with whom agreements are sought in order to maintain historic fishing rights - specially in the North Atlantic - or in order to develop new fishing grounds - specially along the West African coast and in the Indian Ocean - a quarter of the EEC catch is made outside Community waters. France is deeply committed to the orientations of the EEC fisheries policy due to the importance of its fleet of trawlers fishing outside French waters and to the potential catch in the exclusive economic zone of its departments and territories overseas. The compromise signed by member states in 1983 is an important step towards the establishment of a true « Europe Fisheries »

Can continental bogs with stand the pressure due to climate change?

Not all peatlands are alike. Theoretical and process based models suggest that ombrogenic, oligotrophic peatlands can withstand the pressures due to climate change because of the feedbacks among ecosystem production, decomposition and water storage. Although there have been many inductive explanations inferring from paleo-records, there is a lack of deductive empirical tests of the models predictions of these systems’ stability and there are few records of the changes in the net ecosystem carbon balance (NECB) of peatlands that are long enough to examine the dynamics of the NECB in relation to climate variability. Continuous measurements of all the components of the NECB and the associated general climatic and environmental conditions have been made at the Mer Bleue (MB) peatland, a large, 28 km2, 5 m deep, raised ombro-oligotrophic, shrub and Sphagnum covered bog, near Ottawa, Canada from May 1, 1998 until the present. The sixteen-year daily CO2, CH4, and DOC flux and NECB covers a wide range of variability in peatland water storage from very dry to very wet growing seasons. We used the MB data to test the extent of MB peatland’s stability and the strength of the underlying key feedback between the NECB and changes in water storage projected by the models. In 2007 we published a six-year (1999-2004) net ecosystem carbon balance (NECB) for MB of ∼22 ± 40 g C m-2 yr-1, but we have since recalculated the 1998-2004 NECB to be 32 ± 40 g C m-2 yr-1 based on a reanalyzed average NEP of 51 ± 41 g C m-2 yr-1. Over the same period the net loss of C via the CH4 and DOC fluxes were -4 ± 1 and -15 ± 3 g C m-2 yr-1. The 1998-2004 six-year MB average NECB is similar to the long-term C accumulation rate, estimated from MB peat cores, for the last 3,000 years. The post 2004 MB NEP has increased to an average of ∼96 ± 32 g C m-2 yr-1 largely to there being generally wetter growing seasons. The losses of C via DOC (18 ± 1 g C m-2 yr-1) and CH4 (7 ± 4 g C m-2 yr-1) while showing considerable year-to-year variability are not significantly different post 2004. Hence, the proportional loss of C as DOC and CH4 in the MB NECB is slightly less post-2004 than it was before 2004 though the cumulative errors preclude statistically differences. As a result the MB NECB has increased to 79 ± 29 g C m-2 yr-1 post 2004 yielding a 14 year contemporary NECB of 56 ± 36 g C m-2 yr-1, which is double the long-term accumulation rate of C. The variability in the annual NECB and growing season mean NEP for the MB bog can be explained (r2 = 0.35, p \u3c 0.01) by the variability in growing season water table depth. These results suggest the carbon balance – water table feedback is sufficient enough to create stability in continental bogs so they will withstand a considerable amount of climate change

Long-term nutrient addition increased CH4 emission from a bog through direct and indirect effects

Peatlands are globally significant sources of atmospheric methane (CH4). While several studies have examined the effects of nutrient addition on CH4 dynamics, there are few long-term peatland fertilization experiments, which are needed to understand the aggregated effects of nutrient deposition on ecosystem functioning. We investigated responses of CH4 flux and production to long-term field treatments with three levels of N (1.6-6.4 g m(-2) yr(-1) as NH4NO3), potassium and phosphorus (PK, 5.0 g P and 6.3 g K m(-2) yr(-1) as KH2PO4), and NPK in a temperate bog. Methane fluxes were measured in the field from May to August in 2005 and 2015. In 2015 CH4 flux was higher in the NPK treatment with 16 years of 6.4 g N m(-2) yr(-1) than in the control (50.5 vs. 8.6 mg CH4 m(-2) d(-1)). The increase in CH4 flux was associated with wetter conditions derived from peat subsidence. Incubation of peat samples, with and without short-term PK amendment, showed that potential CH4 production was enhanced in the PK treatments, both from field application and by amending the incubation. We suggest that changes in this bog ecosystem originate from long-term vegetation change, increased decomposition and direct nutrient effects on microbial dynamics.Peer reviewe

Tests d'évaluation du degré de pollution des sédiments marins : effets sur la production de larves et la consommation d'algues chez le copépode Tigriopus brevicornis

L'eau interstitielle ou l'eau de lessivage d'un sédiment est mise en contact avec des lots de 50 femelles ovigères du copépode Tigriopus brevicornis. Notons que ce microcrustacé marin est sensible à la pollution mais résistant aux caractéristiques physico-chimiques des types d'eaux testés (salinité et température notamment). On évalue ensuite les effets de ces eaux sur la production larvaire en 10 jours et sur l'ingestion en 4 jours par les copépodes d'une suspension de Phaeodactylum tricornutum. Nous observons ici, pour des lots de sédiments provenant de la région de Marseille, des réductions de la production de larves variant de 61 % (Les Embiez) à 90 % (Vaine). Le test "consommation d'algues", bien moins sensible aboutit pour les mêmes stations à des réductions de 19 % à 35 %. Le test "production larvaire" du fait de sa plus grande sensibilité doit être préféré au test "consommation d'algues".Most pollutants discharged into the sea are found in sediments, generally after temporary fixation in planktonic organisms. The slightest discharge leaves a trace in the soft bottoms. Thus, it may be said that these behave as good "data storage indicators" testifying to the degree of pollution present. Sediments therefore represent a privileged field in research on the state of pollution in the aquatic ecosystem. How can the degree of pollution in this field be evaluated?A chemical analysis of pollutants in sediments is a good means of investigation to detect of degradation in the quality of waters. Most pollutants however are difficult to detect and dose. Moreover, in many cases dosage is tedious and costly. It is from this point of view that biological assays were considered essential.Interstitial water or water used to wash a sediment was placed in contact with batches of 50 ovigerous females of the copepod Tigriopus brevicornis. This marine microcrustacean is known to be sensitive to pollution, though resisting the physical and chemical effects of the waters tested (salinity and temperature, in particular). An evaluation was the made on the effects of these waters; first on larval production during a period of ten days, and then on ingestion by copepeds of a suspension of Pheodactylum tricornutum for four days.The results obtained here with batches of sediment from the Marseilles region show that the larval production test is the most sensitive one. Indeed, the inhibition percentages found by the larval production test range from 35 to 100 % (figure 1), whereas they vary from 5 to 55 % with the algae consumption test (figure 2). With the larval production test, it is possible to classify sediments according to their ecological quality.From this test, moreover, the presence of harmful substances in the sediments can be rapidly detected. Being reproductible and not expensive, it supplements the far too restrictive traditional chemical analyses. When applied to estuarine sedimentary zones, combined with other tests, it should help establish a quality coefficient for sediments based on experimentation