Zooplankton Biomass Depletion Event Reveals the Importance of Small Pelagic Fish Top-Down Control in the Western Mediterranean Coastal Waters

The influence of hydrochemistry and trophic conditions on the coastal zooplankton community’s biomass and metabolic activities was investigated along the Spanish Mediterranean coastal waters, from Algeciras Bay to Barcelona, from autumn 2011 to autumn 2012. Two hydrographic regions were differentiated: NW Alboran (ALB) and W Mediterranean (MED). Zooplankton metabolism was assessed from measurements of the electron transport system (ETS) and aminoacyl-tRNA synthetases (AARS) activities, as proxies for potential respiration and somatic growth, respectively. Zooplankton showed three to fivefold higher biomass in ALB than in MED during autumn 2011 and spring 2012. However, in autumn 2012, a drastic decrease in biomass standing stock was observed in ALB, with no significant differences between the two regions. This biomass depletion event was not associated with environmental variables, food availability or zooplankton metabolic rates, but coincided with a twofold peak of Sardina pilchardus landings in ALB. A reduced standing stock coupled with high zooplankton growth rates suggests mortality by predation as the main cause for the low zooplankton biomass typically observed in MED, and in ALB during autumn 2012.Versión del edito

Description de deux nouvelles espèces de phlébotomes du sous-genre

Les auteurs décrivent deux nouvelles espèces de phlébotomes de région subandine de Bolivie, (alt. : 400-2000 m). Elles appartiennent au sous-genre Helcocyrtomyia, dont font partie les vecteurs d'"uta" au Pérou. Lutzomyia guderiani n. sp., qui appartient au groupe sanguinaria, est une espèce anthropophile de forêt primaire et de caféières dans les Yungas. L. rispaili n. sp., décrite du seul sexe mâle, est apparentée au groupe peruensis ; elle n'a été récoltée qu'en forêt primaire subandine de l'Alto Beni, au-dessous de 1000 m

Influence of the water treatment on the xylem anatomy and functionality of current year shoots of olive trees

Ihc2010 Proceedings Paper 28th Int Horticultural Congress on Science and Horticulture for People (IHC) / Int Symposium on Climwater - Horticultural Use of Water in a Changing Climate Aug 22-27, 2010 Lisbon, PORTUGAL Int Soc Hort Sci (ISHS)International audienceFrom May to October 2006 we applied two water treatments in an olive orchard in south Spain with 38-year-old 'Manzanilla' trees at 7x5 m spacing: a) rainfed, with rainfall as the only source of water supply; b) FAO, in which the trees were drip-irrigated daily from May to September, to replace the crop water needs. The aim of this work was to evaluate the influence of the water treatments on both the anatomical characteristics and the hydraulic performance of the xylem of current-year shoots. In November, 3 cm long segments were taken at 5 cm from the base of current-year shoots of each treatment. Part of these samples was used for hydraulic conductivity (K-h, g m MPa-1 s(-1)) measurements with a hydraulic conductivity meter designed and built in our group. The rest was cryo-fixed in liquid nitrogen for observation by cryo-scanning electron microscopy (cryo-SEM), which allowed us to determine vessel density (vessels mm(-2)) and vessel distribution per diameter classes, at 2 mu m diameter intervals. The xylem water potential (Psi(xylem)) of each sample was also measured, at shoot sampling. The anatomical analysis showed no differences between treatments in vessel density. From the amount of vessel, rainfed trees showed narrower vessels than FAO trees. This may explain the lack of differences in K-h found between the two studied treatments. In fact, the incidence of cavitation is smaller in vessels of reduced diameter. In addition, any reduction in diameter implies a reduced collective pit area between vessels, which reduces the incidence of embolism due to air-seeding. Therefore, the greater number of vessels with reduced diameter induced by the greater water stress suffered by the rainfed trees may have been the major reason for maintaining similar hydraulic conductivities in those trees than in drip-irrigated olive trees

Physiological and genetic response of olive leaves to water stress and recovery: implications of mesophyll conductance and genetic expression of aquaporins and carbonic anhydrase

28th Int Horticultural Congress on Science and Horticulture for People (IHC) / Int Symposium on Climwater - Horticultural Use of Water in a Changing Climate Aug 22-27, 2010 Lisbon, PORTUGAL Int Soc Hort Sci (ISHS)International audienceDrought is considered to be the main environmental factor limiting photosynthesis (A(N)) and, consequently, plant growth and yield worldwide. During photosynthesis, the pathway of CO2 from the atmosphere to the site of carboxylation in the chloroplast stroma has two main components: stomatal (g(s)) and mesophyll (g(m)) conductances. Both are finite and dynamic, responding to many abiotic factors, therefore reducing CO2 concentration. However, little is known about g(m) regulation in the short term, where a possible role of aquaporins (AQP) and carbonic anhydrase (CA) has been proposed. Five-year-old olive trees growing in 50 L pots were used to evaluate the acclimation and recovery of A(N) to drought and subsequent re-watering. Control trees were well-irrigated, while in stressed trees irrigation was withheld for 13 days and then resumed. We made a simultaneous analysis of the genetic expression of two AQP, OePIP1.1 and OePIP2.1, and of CA, on the one hand, and leaf water status, leaf gas exchange and shoot hydraulic conductivity on the other. This is the first time that genetic expression in olive is related to main physiological variables. Two days after withholding irrigation (a.w.i.), the g(s) and g(m) values in Stress tress were lower than in Control trees. This limited photosynthesis. Leaf water status decreased from day 4 a.w.i. Midday leaf water potential dropped from -1.2 on the day before withholding irrigation to -6.0 MPa on day 9 a.w.i. CA expression decreased during drought and there was a peak on OePIP1.1 expression on day 4 a.w.i. Leaf water status recovered in ca. 36 h after resuming irrigation. Both g(m) and A(N) did not fully recover until 46 days after rewatering. Stomatal conductance, however, did not recover in that period, probably because of an irreversible loss of shoot hydraulic conductivity. Both OePIP1.1 and OePIP2.1 peaked 36 h after rewatering. We found significant correlations between g(m) and both OePIP2.1 and CA expression

Use of maximum trunk diameter measurements to detect water stress in mature 'Arbequina' olive trees under deficit irrigation

Olive is one of the fruit tree species for which measurements of the trunk diameter variation (TDV) has shown a lower potential both for monitoring water stress and for scheduling irrigation. This is particularly true in the case of old, big olive trees with heavy fruit load. Fernández et al. (2011, J. Environ. Exp. Bot. 72, 330-338) observed that the daily difference for maximum trunk diameter between deficit irrigated 'Manzanilla' olive trees and control trees growing under non-limiting soil water conditions, termed DMXTD, is more sensitive and reliable for detecting the water stress of the trees than other widely used TDV-derived indices. However, they considered their results as preliminary because of the lack of replications. The aim of this work was to evaluate the usefulness of the DMXTD index for detecting plant water stress in an orchard with 12-year-old 'Arbequina' olive trees with heavy fruit load. The performance of DMXTD for detecting water stress of the trees was compared to that of the signal intensity for the maximum daily shrinkage (SI-MDS) derived from the same TDV records. Results showed that SI-MDS was not useful for indicating the water stress of the trees. On the other hand, the dynamics of DMXTD mimicked those of the soil and plant water status. Four instrumented trees per treatment (replicates) were enough to reduce the uncertainty of the TDV measurements to a reasonable level. Our results show that DMXTD is a useful index to detect the onset, and severity, of water stress in mature 'Arbequina' olive trees with heavy fruit load. They also suggest a potential of DMXTD for scheduling low frequency deficit irrigation strategies.Dendrometer Irrigation scheduling Maximum daily shrinkage Signal intensity Tree water status