The interrelationships among trace element cycling, nutrient loading, and system complexity in estuaries: A mesocosm study

Abstract

Biogeochemical interactions between a suite of trace elements and nutrients were examined in a series of experimental mesocosm experiments to understand how multiple stressors affect estuarine environments and how these effects are modified by the complexity of the system used to examine them. Experimental treatment included additions of nutrients and trace elements separately and combined, along with a gradient in experimental system complexity. Eight mesocosm experiments were carried out from 1996 through 1998. Increased nutrients generally decreased dissolved trace element concentrations, in large part through an increase in phytoplankton biomass, but also by increasing the concentration of metals in the particles. Trace element additions increased dissolved nutrients by decreasing phytoplankton biomass. The presence of sediments reduced both dissolved trace element and nutrient concentrations. Other complexity treatments had weaker effects on both dissolved nutrients and trace elements. Many of the observed effects appeared to be seasonal, occurring only in spring, or their magnitude was greater in spring. This may be linked to a change from phosphorus to nitrogen limitation that often occurs in the Patuxent River estuary in the late spring or early summer period.

Contrasting biogeochemistry of six trace metals during the rise and decay of a spring phytoplankton bloom in San Francisco Bay

“…Mesocosm studies have confirmed those findings by adding nutrients to stimulate a bloom under controlled conditions. For example, Riedel and Sanders (2003) found that dissolved Zn was depleted in mesocosm studies with Patuxent River water, and Wang et al (2005) showed that phytoplankton accumulated Zn from Hong Kong coastal waters. The contrasting results in our study could be because (1) sampling started too late to capture a Zn drawdown, (2) Zn was rapidly repartitioned from the particulate phase, (3) organic complexation limited Zn bioavailability, or (4) a combination of these factors.…”

“…Along with nutrients, trace metals have also been depleted by blooms in South Bay , the Scheldt estuary (Zwolsman and van Eck 1999), coastal waters (Schoemann et al 1998;Ingri et al 2004), and laboratory mesocosm studies (Beck et al 2002;Riedel and Sanders 2003;Wang et al 2005). In South Bay, the 1994 spring bloom depleted dissolved Cd, Ni, and Zn (but not Cu) from the water .…”

“…However, the number of such studies is limited by both the difficulty of capturing a bloom in the field and attributing any observed changes in metal concentrations to bloom processes . Because of these difficulties, some researchers have used mesocosm studies (Beck et al 2002;Riedel and Sanders 2003;Wang et al 2005) or large field enclosures (Muller et al 2005) to study the effect of phytoplankton blooms on metal concentrations.…”

Top-down and bottom-up control of infauna varies across the saltmarsh landscape

“…Coastal ecosystems are becoming increasingly threatened as humans exploit resources and alter habitats (Vituosek et al, 1997;Jackson et al, 2001), and understanding multifactor anthropogenic-induced change is a priority (Riedel and Sanders, 2003;Wiegner et al, 2003). It is therefore important for coastal resource managers, conservationists and ecologists alike to know if the assumptions listed above compromise our understanding of anthropogenic effects.…”

Increasing copper alters cellular elemental composition (Mo and P) of marine diatom

“…P is one of backbone elements involving the synthesis of basic structure such as membranes, while Mo is involved in forming active centers of enzymes catalyzing nitrate reduction and nitrogen fixation. In phytoplankton, trace elements commonly interact with each other during biological uptake due to ion competition and/or detoxification (Interlandi, ; Riedel & Sanders, ; Serra, Guasch, Admiraal, Van der Geest, & Van Beusekom, ; Wang & Dei, ). Hall, Healey, and Robinson () observe that P is involved in excluding/eliminating toxic metals from cells in cultures of Chlorella vulgaris .…”