Species-specific variation in the phosphorus nutritional sources by microphytoplankton in a Mediterranean estuary

We investigated the species-specific phosphorus (P) nutrition sources in the microphytoplankton community in the Mahon estuary (Minorca, Western Mediterranean) in 2011, under two contrasting hydrographic scenarios. Estuarine flow, nutrient concentrations, phytoplankton community composition and enzyme-labeled fluorescence (ELF) were measured in June and October, corresponding to the beginning and the end of summer. Dissolved inorganic nitrogen (DIN) and inorganic phosphate (Pi) exhibited enhanced concentrations in the inner estuary where N:P molar ratios suggested P-limitation in both surveys. Pi was low and variable (0.09±0.02 μmol•l-1 in June and 0.06±0.02 μmol•l-1 in October), whereas organic phosphorus remained a more reliable P source. Even though ambient Pi concentrations were slightly higher on June, when the microphytoplankton assemblage was dominated by dinoflagellates, the percentage of cells expressing ELF labeling was notably higher (65% of total cells) than in October (12%), when the presence of diatoms characterized the microphytoplankton community. ELF was mainly expressed by dinoflagellate taxa, whereas diatoms only expressed significant AP in the inner estuary during the June survey. A P-addition bioassay in which response of AP to Pi enrichment was evaluated showed remarkable reduction in AP with increasing Pi. However, some dinoflagellate species maintained AP even when Pi was supplied in excess. We suggest that in the case of some dinoflagellate species AP is not as tightly controlled by ambient Pi as previously believed. AP activity in these species could indicate selective use of organic phosphorus, or slow metabolic response to changes in P forms, rather than physiological stress to low Pi availability. We emphasize the importance of identifying the links between the different P sources and the species-specific requirements, in order to understand the ecological response to anthropogenic biogeochemical perturbations

The relation between values and prosocial behavior.

Pētījuma mērķis ir noskaidrot, kāda ir vērtību saistība ar 4 prosociālas uzvedības veidiem (altruistisko, publisko, anonīmo un emocionālo), kā arī – vai pastāv vērtību un prosociālās uzvedības atšķirības skolotāju un studentu izlasēs. Pētījumā piedalījās 119 4.-10. klašu skolotāji un 158 pēdējo kursu studenti. Izmantojot Švarca vērtību aptauju (SVS, Schwartz Value Survey, Schwartz, 1992; adaptēta Latvijā – Austers, 2002) un prosociālo tendenču aptaujas (Prosocial Tendencies Measure-Revised, PTM-R, Carlo & Randall, 2002) modificēto versiju latviešu valodā (modifikācija veikta šajā pētījumā), tika atklātas saistības starp vērtībām un prosociālo uzvedību abās izlasēs. Pārsteidz pozitīvā saistība starp pašrealizāciju un altruistisko prosociālo uzvedību studentu izlasē. Tika atklātas atšķirības vērtībās un prosociālajā uzvedībā starp abām izlasēm (atšķirības netika atklātas paštranscendences vērtībās), kā arī prosociālajā uzvedībā. Atslēgas vārdi: vērtības, prosociāla uzvedība.The aim of this study is to find out the link between values and four types of prosocial behavior (altruistic, public, anonimous and emotional) and also to answer the question – is there any differencies between teacers and students in values and prosocial behavior. The respondents were 119 4th-10th grade teachers and 158 undergraduates. Using Schwartz Value Survey (SVS, Schwartz, 1992; potted to Latvian condition Austers, 2002) and Prosocial Tendencies Measure-Revised (PTM-R, Carlo & Randall, 2002) modifyed in Latvian (in this study) was found the connection between values and prosocial behavior in both groups. It is surprising that there exists positive correlation between self-direction and altruistic prosocial behavior. There were found differencies in values and prosocial behavior between teachers and students (there is no difference in self transcendence values between both groups) and prosocial behavior. Key words: values, prosocial behavior

Species-specific variation in the phosphorus nutritional sources by microphytoplankton in a Mediterranean estuary

[eng] We investigated the species-specific phosphorus (P) nutritional strategies in the microphytoplankton community in the Mahon estuary (Minorca, Western Mediterranean) in 2011, under two contrasting hydrographic scenarios. Estuarine flow, nutrient concentrations, phytoplankton community composition and enzyme-labeled fluorescence (ELF) were measured in June and October, corresponding to the beginning and the end of summer. Dissolved inorganic nitrogen (DIN) and inorganic phosphate (Pi) exhibited enhanced concentrations in the inner estuary where N:P molar ratios suggested P-limitation in both surveys. Pi was low and variable (0.09±0.02 µmol L-1 in June and 0.06±0.02 µmol L-1 in October), whereas organic phosphorus remained a more readily available P source. Even though ambient Pi concentrations were slightly higher on June, when the microphytoplankton assemblage was dominated by dinoflagellates, the percentage of ELF labeled cells was notably higher (65±9% of total cells) than in October (12±10%), when the presence of diatoms characterized the microphytoplankton community. Alkaline phosphatase activity (AP) was mainly expressed by dinoflagellate taxa, whereas diatoms only displayed significant AP in the inner estuary during the June survey. A P-addition bioassay in which response of AP to Pi enrichment was evaluated showed marked reduction in AP with increasing Pi. However, some dinoflagellate species maintained AP even when Pi was supplied in excess. We suggest that in the case of some dinoflagellate species AP is not as tightly controlled by ambient Pi as previously believed. AP activity in these species could indicate selective use of organic phosphorus, or slow metabolic response to changes in P forms, rather than physiological stress to low Pi availability. We emphasize the importance of identifying the species-specific phosphorus requirements and their capability for P assimilation in order to understand the contribution of microphytoplankton to the whole community response to biogeochemical perturbations