Francisco A. Comín

Scientific Foundations for an IUCN Red List of Ecosystems

An understanding of risks to biodiversity is needed for planning action to slow current rates of decline and secure ecosystem services for future human use. Although the IUCN Red List criteria provide an effective assessment protocol for species, a standard global assessment of risks to higher levels of biodiversity is currently limited. In 2008, IUCN initiated development of risk assessment criteria to support a global Red List of ecosystems. We present a new conceptual model for ecosystem risk assessment founded on a synthesis of relevant ecological theories. To support the model, we review key elements of ecosystem definition and introduce the concept of ecosystem collapse, an analogue of species extinction. The model identifies four distributional and functional symptoms of ecosystem risk as a basis for assessment criteria: A) rates of decline in ecosystem distribution; B) restricted distributions with continuing declines or threats; C) rates of environmental (abiotic) degradation; and D) rates of disruption to biotic processes. A fifth criterion, E) quantitative estimates of the risk of ecosystem collapse, enables integrated assessment of multiple processes and provides a conceptual anchor for the other criteria. We present the theoretical rationale for the construction and interpretation of each criterion. The assessment protocol and threat categories mirror those of the IUCN Red List of species. A trial of the protocol on terrestrial, subterranean, freshwater and marine ecosystems from around the world shows that its concepts are workable and its outcomes are robust, that required data are available, and that results are consistent with assessments carried out by local experts and authorities. The new protocol provides a consistent, practical and theoretically grounded framework for establishing a systematic Red List of the world’s ecosystems. This will complement the Red List of species and strengthen global capacity to report on and monitor the status of biodiversity

Interactive effects of N and P on growth, nutrient allocation and NH4 uptake kinetics by Phragmites australis

The interactive effects of three levels of NH4‐N (50, 500 and 1000mmol l 1 ) and two levels of phosphate (15 and 50mmol l 1 ) on growth, nutrient allocation and ammonium uptake kinetics by Phragmites australis(Cav.) Trin. ex Steudel were studied in hydroponic culture in the laboratory. Nitrogen level in the root solution significantly affected the relative growth rate of the plants, the rate being lower at low N (0.026 per day) than at intermediate (0.035 per day) and high N (0.037 per day), but phosphorus did not significantly affect growth. The N : P ratio in the root solution significantly affected the growth rate which was highest at N : P ratios between 10 and 33 on a molar basis. Nitrogen and phosphorus concentration in the plant tissues generally increased with N level in the root solution, but P level had no effect. Plant tissue N : P ratios (on a molar basis) varied between 13.5 in the stems to 28.0 in the leaves and were unaffected by the treatments. Ammonium uptake kinetics were unaffected by N treatment, but Vmax was significantly affected by P treatment averaging (mean 95% confidence limits (CL)) 151 44mmol g 1 root dry weight h 1 in the low-P treatment and 229 70mmol g 1 root dry weight h 1 in the high-P treatment. The overall mean (95% CL) NH4‐N uptake kinetic parameters were: Vmax = 190 20mmol g 1 root dry weight h 1 ;K 1=2 = 21.8 1.8mmol l 1 , and Cmin = 1.2 0.2mmol l 1 . Mean (SD) root respiration rate was 72 22mmol CO2 g 1 dry weight h 1 and was unaffected by the treatments. The results of the study support the general hypothesis that P. australis is well-adapted for growth in nutrient-rich habitats. However, P. australis is able to acclimate to low nutrient availability by increasing the affinity for ammonium uptake. ©1999 Elsevier Science B.V. All rights reserved.

Nitrogen cycling networks of coastal ecosystems: influence of trophic status and primary producer form

Abstract We have used ecological network analysis to compare nitrogen cycles from five well-researched coastal ecosystems. These included a representative ricefield and two lagoons (Tancada and Encanysada lagoons) in the Ebro River delta, Spain; a region of the Sacca di Goro, a lagoon at the mouth of the Po River, Italy; and a drowned river estuary in North Carolina, USA, the Neuse River estuary. We constructed networks for the various systems and ranked them by trophic status (i.e., degree of eutrophication) using four indices. We then considered the importance of (1) trophic status, (2) growth form of dominant primary producer and (3) water residence time to the intensity and pattern of recycling and to the manner in which the systems can “filter” N. Three indices of flux (rate of import, primary producivity and total systems throughput) gave similar rankings of trophic status among ecosystems with the Italian and U.S. systems being most eutrophic, ricefields next, and then the two Spanish lagoons. Patterns of N export and of cycling within the systems were most closely related to the growth form of dominant primary producers. Phytoplankton, with their rapid turnover rate, foster rapid recycling within the water column and continuous transfer to sediments and export. Submersed and emergent aquatic vegetation and macroalgae create lags and pulses within systems by sequestering N during growth and releasing it during senescence, death and decomposition. Trends in cycling among systems relative to trophic status or water residence appear largely secondary to primary producer growth form.

A comparative study of the effect of pH and inorganic carbon resources on the photosynthesis of three floating macroalgae species of a Mediterranean coastal lagoon.

This study examines the effect of pH changes on photosynthetic characteristics and the role of dissolved inorganic carbon (DIC) in determining the dominance of three species of macroalgae Chaetomorpha linum (O.F. Müller) Kützing, Gracilaria verrucosa (Hudson) Papenfuss and Ulva sp. in a Mediterranean coastal lagoon. Fluctuations of pH were measured in the lagoon in summer. Water column CO(2) and HCO(3)(-) concentrations inside the algal mat showed significant diurnal fluctuations, from a morning peak to an afternoon low, decreasing 96 and 40%, respectively. The response of photosynthesis to increased pH was examined in laboratory conditions in spring (May) and summer (July). The photosynthetic rate declined rapidly at pH above 8.5 and below 6.5. G. verrucosa responded differently in spring and summer showing acclimation to higher pH in summer than in spring. In Ulva sp. incubations, we observed optimum photosynthesis between pH 6 and 7.5. The decrease in photosynthetic rate below pH 6 was lower (12.30%) than above pH 8 (81.03%). This difference may be related to the origin of the macroalgae, suggesting acclimation to the original pH of the environment. Results from instantaneous photosynthesis measurements indicate that low DIC-availability limits the photosynthetic capacity of G. verrucosa, C. linum and Ulva sp. in spring and of C. linum at high irradiances in summer. Our results also show that G. verrucosa has a higher efficiency at low CO(2) concentrations than C. linum and Ulva sp. It is suggested that G. verrucosa may be better adapted to maintain higher photosynthetic rates than other macroalgae in conditions of tissue N sufficiency and low water DIC concentrations which are typical of shallow coastal environments in summer.

Restored wetlands as filters to remove nitrogen

Four wetlands established in abandoned ricefields and dominated by Phragmites australis, Typha latifolia and Scirpus lacustris were used to improve the quality of agricultural runoff in the Ebro Delta (NE Spain) in 1993, 1994 and 1995. The wetlands were continuously flooded with water from a ricefield irrigation network during the growing season and received water with between 5 and 200 mg N m−2 d−1 in the form of dissolved inorganic nitrogen (DIN), between 0 and 67 mg N m−2 d−1 in the form of dissolved organic nitrogen (DON) and between 1.2 and 225 μg M−2 d−1 in the form of particulate nitrogen (PN). Surface N outflows contained between 0 and 12 mg N m−2 d−1 of DIN, between 1 and 86 mg N m−2 d−1 of DON and between 1 and 40 μg m−2 d−1 of PN. The nitrogen retention efficiency was always positive 100% of the input, except for DON and PN at low inlet loadings. The emergent macrophytes accumulated between 20 and 100 mg N m−2 d−1, which accounted for between 66 and 100% of the inflowing DIN. The removal rate constants calculated according to first-order plug-flow kinetics, were between 0.003–0.09 m day−1 for total nitrogen, and 0.005–0.3 m day−1 for DIN. Plant uptake, detritus accumulation and decomposition, and nitrogen recycling in the sediment are the major processes which could explain nitrogen retention in the wetlands. Wetlands restored from ricefields act as highly efficient water polishing filters for agricultural runoff and, at the same time, can contribute to the habitat biodiversity of large areas where rice is cultivated extensively.

Spanish salt lakes: Their chemistry and biota

A large number of small saline lakes are distributed throughout Spain. Four main lake districts occur from sea level to 1000 m.a.s.l. Most lakes are temporary because of the arid conditions in the Spanish endorheic areas. Many lakes are situated in Tertiary depressions in NE. and S. Spain. Lake basins were formed in karstic areas by hydrologic and aeolian erosion. Saline lakes in NE. Spain occupy areas isolated between river basins. The major ions encountered in these lakes are usually sodium-chloride and magnesium-sulphate; sodium carbonate or sodium-sulphate rich waters also occur.

Effect of climatic gradients on the photosynthetic responses of four Phragmites australis populations

Four populations of Phragmites australiscollected from geographically distinct areas in Europe were propagated in outdoor experimental plots at four sites with dissimilar climate (Denmark, The Netherlands, Spain and Czech Republic). During the second growing season the photosynthetic characteristics of Phragmites leaves were evaluated under controlled conditions for each site, each population, and their interaction, and related to tissue nutrient and pigment content. The light-saturated rate of photosynthesis ( Pmax), dark respiration rate (Rd), light compensation point (Ic), and apparent quantum efficiency ( i) were significantly affected by growth site, whereas differences between populations were less pronounced. Plants grown in the more northerly climates appeared to be more photosynthetically limited through lower Pmax values and lower i levels, reflecting phenotypic acclimation to the lower summer temperatures and irradiance levels at the northern growth sites. The higher Pmax levels in the southern climate were correlated with higher nutrient levels in the tissue of leaves. The study shows that the four genetically distinct populations of P. australis exhibited high phenotypic plasticity in photosynthetic response to climatic change. The degree of photosynthetic plasticity within P. australis genotypes is large, and generally larger than the genetically determined differences between European populations. The results are discussed in relation to the prospected global climate change.

Seasonal comparisons of leaf processing rates in two Mediterranean rivers with different nutrient availability

The litter-bag technique was used to study the effect of seasonality (spring–summer versus autumn–winter) and nutrient availability on leaf decomposition in two Mediterranean watercourses: the Ebro river, which is eutrophic, and the Sènia stream. To establish the effect of macroinvertebrates on litter breakdown, we used air-dried leaves from the two dominant species of riparian vegetation (Populus alba and Populus nigra) along each watercourse and litter bags of two mesh sizes (100 μm and 5 mm). Macroinvertebrates were collected from the bags and ash free dry weight and carbon, nitrogen and phosphorus contents of the plant detritus remaining were measured. Litter decomposition rates, in days and degree-days, were estimated using a simple exponential model. A significant effect of macroinvertebrates and seasonality on litter decay was observed only in the Ebro river. Decomposition rates were faster in this river, P. alba showing the highest rates in spring–summer (0.022–0.038 day−1). The macroinvertebrates collected from the bags were mostly collector-gatherers of the genus Chironomus. Their density increased over time and was greater in the experiments performed in spring–summer (two to ten fold higher). Higher temperatures together with increased macroinvertebrate densities led to augmented decomposition rates in the Ebro river but no effect was observed in the Sènia stream. Our data show that leaf decay is both quantitatively and qualitatively affected by inorganic nutrient levels and temperature in the ambient environment, regardless of initial C:N and C:P ratios.

EFFECT OF CLIMATE ON THE SALT TOLERANCE OF TWO PHRAGMITES AUSTRALIS POPULATIONS. II. DIURNAL CO2 EXCHANGE AND TRANSPIRATION

This study examined the effects of salinity and climate on instantaneous CO2 exchange rates and daily carbon balance for two populations of Phragmites australis. Plants propagated from seeds collected in Denmark (=Danish population) and Spain (=Spanish population) were grown at salinities of 0, 5 and 10% at outdoor experimental plots situated at a nemoral growth site (Denmark, 56N) and at a mediterranean growth site (Spain, 41N). In situ measurements of shoot CO2 exchange were made under different meteorological conditions. Maximum CO2 uptake rates were 24 and 19mmol m 2 s 1 in Spain and Denmark, respectively, and were only reached under conditions of full sunlight. On sunny days, CO2 uptake was reduced less by salinity at the Spanish site than at the Danish site. Photosynthetic photon flux densities saturating shoot photosynthesis were much lower in Spain (ca. 600mmol m 2 s 1 ) as compared to those in Denmark (ca. 1300mmol m 2 s 1 ). This affected the period of maximum CO2 uptake rates which was 2‐3 h longer at the Spanish growth site, despite shorter day length at this site (15 h) than at the Danish site (17 h). Dark respiration rates of shoots were higher at the Spanish growth site (2‐8mmol CO2 m 2 s 1 ) as compared to the Danish site (less than 2 mmol CO2 m 2 s 1 ). Salinity was observed to accelerate rates of dark respiration only at the Spanish site. Integrals of shoot CO2 exchange rates over a 24 h period indicated lower total daily carbon gain at the Danish site, which under clear sky conditions was 65‐80% of that at the Spanish site. Cloud cover was found to reduce net photosynthetic CO2 uptake considerably and could even cause a net loss of carbon during periods, which in absence of clouds could confer maximum uptake rates. The salt tolerance and productivity of P. australis is therefore strongly related to the ratio of realised to potential sun hours. This ratio may override the importance of other environmental factors such as temperature. This study also evaluated the effects of moderate salinity stress (0‐15% salinity) on in situ P. australis transpiration. Daily transpiration rates were 30‐75% higher at the Spanish site (0.38‐0.56 g H2 Oc m 2 day 1 ) as compared to the Danish site

High-resolution saline lake sediments as enhanced tools for relating proxy paleolake records to recent climatic data series

Abstract Lake level in an endorheic saline lake in Southern Europe has been inferred for the last 105 years (1889–1994) at an annual level of resolution using two independent methods. First, ordination analyses (factor analysis (FA), correspondence analysis (CA) and detrended correspondence analysis (DCA)) have been used to point out the mineral successions of the sedimentary record. These successions are evidenced by the arch disposition of both samples and mineral phases in the plane defined by the first two eigenvectors calculated by these analyses. These temporal evolutions are the same as those obtained during the drying and refilling phases of saline lakes. Relay indices (RI) were obtained from distances to the first two eigenvectors, which accurately reconstructed the lake-level evolution during this period. Second, an inferred lake-level series was obtained using a multivariate time series model from the average maximum temperatures and total rainfall. Six main drought periods were found, which coincided with known droughts in the area. A high level of agreement was found between the two reconstructions, which offered the possibility of directly extending the instrumental record back into the past. Therefore, climatic changes could be reconstructed from saline lakes provided that an accurate chronological control of sedimentary processes is available.