Congruence, but no cascade-Pelagic biodiversity across three trophic levels in Nordic lakes

Covariation in species richness and community structure across taxonomical groups (cross-taxon congruence) has practical consequences for the identification of biodiversity surrogates and proxies, as well as theoretical ramifications for understanding the mechanisms maintaining and sustaining biodiversity. We found there to exist a high cross-taxon congruence between phytoplankton, zooplankton, and fish in 73 large Scandinavian lakes across a 750 km longitudinal transect. The fraction of the total diversity variation explained by local environment alone was small for all trophic levels while a substantial fraction could be explained by spatial gradient variables. Almost half of the explained variation could not be resolved between local and spatial factors, possibly due to confounding issues between longitude and landscape productivity. There is strong consensus that the longitudinal gradient found in the regional fish community results from postglacial dispersal limitations, while there is much less evidence for the species richness and community structure gradients at lower trophic levels being directly affected by dispersal limitation over the same time scale. We found strong support for bidirectional interactions between fish and zooplankton species richness, while corresponding interactions between phytoplankton and zooplankton richness were much weaker. Both the weakening of the linkage at lower trophic levels and the bidirectional nature of the interaction indicates that the underlying mechanism must be qualitatively different from a trophic cascade.

Depression assessed over 1-year survival in patients with myocardial infarction

OBJECTIVE

To estimate the prevalence of ICD-10 depression using a self-reported questionnaire and to examine if depression is associated with increased 1-year mortality in patients with myocardial infarction (MI).

METHOD

In total, 763 MI-patients completed the Major Depression Inventory at discharge. Information from hospital notes was collected and patients were followed 1 year for re-admission and mortality through national registries.

RESULTS

Seventy-three patients (9.6%) were depressed at discharge. Depression was not a significant independent predictor of mortality; however, there was a significant trend for increasing mortality with increasing severity of the depressive state (P = 0.028). All mortality among depressed patients was in patients with non-Q-wave infarction.

CONCLUSION

Ten per cent of MI-patients fulfilled diagnostic criteria for depression at discharge. There was a significant trend for increasing mortality with increasing severity of the depressive episode. All mortality among depressed patients was seen in patients with non-Q-wave infarction. These findings indicate future studies in selected subgroups of MI-patients.

Psychosocial predictors of depression in patients with acute coronary syndrome

OBJECTIVE

To describe the prevalence of depression according to ICD-10 criteria using a self-completed questionnaire and to identify psychosocial predictors of depression at discharge in patients with acute coronary syndrome.

METHOD

A total of 899 patients with acute coronary syndrome completed the Major Depression Inventory at discharge and a questionnaire regarding previous depression and family history of depression. Information concerning civil status was obtained from the Civil Person Registry.

RESULTS

Ninety patients (10%) were depressed according to ICD-10 criteria at discharge with 7.2% having a moderate to severe depression at discharge. Women were significantly more frequently and severely depressed than men. Patients with and without depression reported primarily somatic symptoms of depression. Cardiovascular risk factors or treatment did not differ between patients with and without depression. Previous depression (OR 2.9, 95% CI 1.4-6.0 adjusted) and female gender (OR 2.5, 95% CI 1.5-4.3 adjusted) predicted depression at discharge in a logistic regression model.

CONCLUSION

Somatic symptoms of depression are prevalent in patients with acute coronary syndrome. The use of self-completed non-diagnostic questionnaires assessing symptoms of depression therefore is cautioned as patients may wrongly be identified as depressed. In patients with acute coronary syndrome depression is predicted by well-known psychosocial risk factors.