Use of amino acid composition to investigate settling and resuspension of a spring bloom in the southern Skagerrak

Abstract

Short-term changes in amino acid composition of near-bed particulate flux were studied at an upper shelf location in the southern Skagerrak, 55 m deep. Sediment trap samples were collected with a 3-d sampling interval from late April to late June 1992. A high settling rate (85 g m Ϫ2 d Ϫ1 ) was intercepted in May, coinciding with high shear velocity and settling of fresh phytoplankton. During the peak in the settling rate, a decrease in the mole percentage of glycine was noticed. At the end of June, smaller peaks of high flux corresponded to periods of increased shear velocity; during this time, the amino acid composition did not change. A Q-mode factor analysis on the amino acid variation of collected particles showed a relation between certain samples consisting of fresh phytoplankton material. If organic carbon is compared to the shear velocity, the related phytoplankton samples had a positive correlation, whereas the more degraded samples had a negative correlation. The observed patterns suggest a coupling between food web dynamics and particle composition on the one hand and availability of benthic fluff at the sediment surface on the other. The length of the period affected by fresh material could be sorted out by using the amino acid composition and be made comparable to samples influenced by more degraded material.Shelves and slopes are highly dynamic environments where the chemical composition of settling particulate matter and the movement of phytoplankton through the water column is controlled by physical processes such as turbulence, advection, gravitational sinking, and sorting, especially during bloom periods in spring and late summer (Riegman et al. 1993). The water content and consistency of the sediment surface layer change because of different conditions, and a surficial fluff layer, benthic fluff, can develop when sedimentation is greater than erosion. Newly settled material with a high water content and/or material with a low density results in benthic fluff that is less resistant to erosion. Jago and Jones (1998) showed that during periods with strong bottom currents, the supply of resuspendable material on the bottom limits the amount being resuspended and transported.

Different Biochemical Compositions of Particulate Organic Matter Driven by Major Phytoplankton Communities in the Northwestern Ross Sea

“…These two groups formed high proportions of CHO and high C/N values with a haptophytes-abundant group dominated by solitary P. antarctica cells while relatively higher proportions of PRT and high EAAI scores with diatom-dominant communities ( Figure 6 ). In the PC2, EAA composition and DI score were negatively related to glycine which is considered as an indicator of organic matter degradation as discussed above ( Figure 6 ) ( Liebezeit and Bölter, 1986 ; Petersson and Floderus, 2001 ). Overall, our results revealed that the southern region dominated majorly by micro-sized diatoms was positively correlated with PRT, EAA, and EAAI indicating a good protein quality, while the relatively solitary P. antarctica- abundant northern region with higher CHO contribution was negatively correlated with good protein quality factors.…”

Biochemical nutrient requirements of the rotifer Brachionus calyciflorus: co‐limitation by sterols and amino acids

“…). As amino acid profiles of natural food sources vary seasonally, (Cowie & Hedges ; Petersson & Floderus ; Kalachova et al . ), the performance of freshwater herbivores might be constrained not only by a low availability of essential dietary lipids, but also by the availability of certain amino acids, which potentially results in a simultaneous limitation by multiple nutrients.…”

“…Moreover, it has been suggested that specific dietary amino acids, in particular arginine and histidine, are involved in triggering the switch between reproductive modes in Daphnia, that is, they have been found to avert crowding-induced resting egg production and to enhance subitaneous reproduction (Koch et al 2011). As amino acid profiles of natural food sources vary seasonally, (Cowie & Hedges 1992;Petersson & Floderus 2001;Kalachova et al 2004), the performance of freshwater herbivores might be constrained not only by a low availability of essential dietary lipids, but also by the availability of certain amino acids, which potentially results in a simultaneous limitation by multiple nutrients.…”

ENSO related variations in biogeochemistry of AA and HA in settling particles along the equatorial Pacific Ocean

“…Since plankton species composition affects the efficiency of the biological carbon pump (Dandonneau et al, 2004), a change in plankton diversity may be reflected in minor changes in AA and HA compositions of settling particles, as revealed by the discriminant analysis. In a few recent studies, changes in AA composition have been attributed to the changes in planktonic diversity (Braven et al, 1995;Petersson and Floderus, 2001;Kalachova et al, 2004;Brucet et al, 2005).…”

“…However, there are some AAs which decompose at a faster rate than other AAs, and thus produce markers for monitoring the decomposition of OM in time and space due to microbial enzymatic action. For instance, the ratios Asp/β-Ala and Glu/γ-Aba have very often been used to give a qualitative estimate of the degradation of OM in environmental samples (e.g., Lee and Cronin, 1982;Henrichs and Farrinton, 1987;Gupta et al, 1997;Petersson and Floderus, 2001;Gupta and Kawahata, 2003a). However, these two ratios sometimes do not complement the trend shown by each individually, as is evident from some low correlation coefficient values between them in this study (Table 3).…”