Spatial and temporal variability in nutrient concentrations in Liverpool Bay, a temperate latitude region of freshwater influence

2011 ◽  
Vol 61 (12) ◽  
pp. 2181-2199 ◽  
Author(s):  
Naomi Greenwood ◽  
David J. Hydes ◽  
Claire Mahaffey ◽  
Andrew Wither ◽  
Jon Barry ◽  
...  
2012 ◽  
Vol 69 (11) ◽  
pp. 1894-1897 ◽  
Author(s):  
C. Rhett Jackson ◽  
Douglas J. Martin

Levi et al. (2011, Can. J. Fish. Aquat. Sci. 68: 1316–1329) related nutrient concentrations before, during, and after spawning, as well as various measures of channel morphology, to levels of prior timber harvest in seven watersheds on Prince of Wales Island in Southeast Alaska, USA. They assumed that single reaches of seven streams were otherwise similar and that other controls on channel morphology and nutrient dynamics could be ignored relative to the effects of prior timber harvest. In this commentary we show that the seven watersheds were not similar and that the sample set was too small to address geomorphic variability unrelated to timber harvest. Levi et al. failed to consider adequately the natural drivers of spatial and temporal variability in channel morphology and to consider stronger alternate hypotheses for observed channel conditions.


Crop Science ◽  
2004 ◽  
Vol 44 (3) ◽  
pp. 847 ◽  
Author(s):  
Weidong Liu ◽  
Matthijs Tollenaar ◽  
Greg Stewart ◽  
William Deen

2020 ◽  
Vol 63 (5) ◽  
pp. 429-438
Author(s):  
Jimena Samper-Villarreal ◽  
Jorge Cortés

AbstractSeagrass conservation and management requires scientific understanding of spatial and temporal variability, information that is currently limited for the Eastern Tropical Pacific (ETP). Here, we analysed seagrass presence based on previous reports, herbarium collections and stakeholder knowledge, combined with field characterization in Golfo Dulce, southern Pacific coast of Costa Rica. Seagrasses were found at multiple locations along a narrow border close to shore and in up to 6 m depth within Golfo Dulce, dating back to 1969. Two seagrass species were found, Halophila baillonii and Halodule beaudettei. Seagrass biomass values for Golfo Dulce (12.0 ± 8.5 g DW m−2) were lower and water nutrient concentrations were higher than previously reported in the gulf. Shoot density (1513 ± 767 shoots m−2) was similar to previous reports. Stable isotope values in seagrass were −11.3 ± 1.0‰ δ13C and 1.2 ± 0.9‰ δ15N; while those in sediments were −26.1 ± 1.3 and 2.5 ± 0.9‰. In Golfo Dulce, isotopic values of both seagrass species do not overlap with other known primary producers. Management strategies should aim to minimize known seagrass stressors, protect potential seagrass habitat, and take into account the dynamic life strategies of the two seagrass species found.


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