Population dynamics of Cyathura carinata (Isopoda) in a eutrophic temperate estuary

Abstract

From January 1993 to September 1995, Cyathura carinata was a target species of a monitoring programme carried in the Mondego Estuary (Portugal). Being one of the key species of the intertidal mud flats, this isopod was found to be most abundant in a eutrophic area, where seasonal macroalgal blooms usually occur. Its density decreased towards downstream areas, where some Zostera noltii beds exist. At the Mondego Estuary, the present work stated that C. carinata: (a) had a 2-year life span, even though, 80-90% of the individuals died when 1 year old, revealing a strong post-reproduction mortality; (b) produced a single cohort per year; (c) showed continuous growth (with lower rates during winter); (d) evidenced protogynous hermaphroditism and (e) presented a high growth production and a low turnover ratio. A latitudinal gradient reflected in the life features of C. carinata was described. Except for the life span and the frequency of reproduction, which are generally valid for all populations, C. carinata from the Mondego Estuary fitted the characteristics of other populations from the south of Europe.The effects of macroalgal blooms were assessed. Cyathura carinata seemed to temporarily benefit from the presence of macroalgae, due to higher energy resources and more efficient protection against predators. In a long term, algal blooms had negative consequences. It was particularly evident on the recruitment success, which had repercussions in population abundance, and on the secondary production. Therefore, repeated events of algal blooms embracing the distribution areas of C. carinata represent a threat to this species in eutrophic estuaries.

The impact of extreme weather events on the seagrass Zostera noltii and related Hydrobia ulvae population

“…This area has less energetic hydrodynamics and is covered seasonally by green macroalgae (Ulva spp.) (Martins et al, 2001;Cardoso et al, 2002Cardoso et al, , 2004Ferreira et al, 2004;Pardal et al, 2004). In the eutrophic area, the H. ulvae population was monitored from January 1993 to January 1997 and again from January 1999 to December 2005.…”

Distribution of endocrine disruptors in the Mondego River estuary, Portugal

“…During its course of 227 km, it runs through rural as well as highly urbanized and industrialized areas before reaching its 1,600 ha estuary, where it becomes visible polluted (Ferreira et al 2004). Its main pollution sources are waste waters, most coming from several sewage treatment plants that give support to approximately 200,000 inhabitants and to different types of industries, and the agricultural run-off, end result of 15,000 ha of cultivated land (mostly rice and corn fields) located upstream the Mondego estuary (Ferreira et al 2004).…”

“…During its course of 227 km, it runs through rural as well as highly urbanized and industrialized areas before reaching its 1,600 ha estuary, where it becomes visible polluted (Ferreira et al 2004). Its main pollution sources are waste waters, most coming from several sewage treatment plants that give support to approximately 200,000 inhabitants and to different types of industries, and the agricultural run-off, end result of 15,000 ha of cultivated land (mostly rice and corn fields) located upstream the Mondego estuary (Ferreira et al 2004). Currently, it is known that the contamination of this estuary increased during the last decade because several pollution indicators have been referred for this area, such as the increase of eutrophication (Lopes et al 2000;Ferreira et al 2004) and the decrease of aquatic biodiversity .…”

“…Its main pollution sources are waste waters, most coming from several sewage treatment plants that give support to approximately 200,000 inhabitants and to different types of industries, and the agricultural run-off, end result of 15,000 ha of cultivated land (mostly rice and corn fields) located upstream the Mondego estuary (Ferreira et al 2004). Currently, it is known that the contamination of this estuary increased during the last decade because several pollution indicators have been referred for this area, such as the increase of eutrophication (Lopes et al 2000;Ferreira et al 2004) and the decrease of aquatic biodiversity . Also, the continuous increase of cutaneous diseases in fish, and sometimes in humans, by mucormycosis, was somehow related to the increase of pollution in this estuary (Coelho et al 2003).…”

Mass balanced models of the food web in three areas along a gradient of eutrophication symptoms in the south arm of the Mondego estuary (Portugal)

“…If a trophic network is defined as a model of energy and material flow between organisms via predation processes, then the adjustment (increase or decrease) of elements from the intricate food web and the changes produced in the community structure by this process should produce a disruption in the trophic structure. From this viewpoint, the main goal of this paper was to construct mass balanced models of the food web in three areas along an eutrophication gradient in the south arm of the Mondego estuary (Portugal), a small and well described temperate intertidal estuary Pardal et al, 2000Pardal et al, , 2004Cardoso et al, 2004;Ferreira et al, 2004;Neto, 2004), using the "Ecopath with Ecosim" software package. This work was a first study of the Mondego estuary using a mass-balance model of trophic interactions.…”