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Wirtz P.,University of Algarve | Brito A.,University of La Laguna | Falcon J.M.,University of La Laguna | Freitas R.,University of Cape Verde | And 4 more authors.
Spixiana | Year: 2013

A check-list of the coastal fishes of the Cape Verde Islands is presented. The species Acantholabrus palloni, Canthigaster supramacula, Carcharhinus leucas, Chaetodipterus lippei, Corniger spinosus, Dasyatis centroura, Didogobius n. sp., Epigonus constanciae, Halobatrachus didactylus, Hemiramphus balao, Leptocharias smithii, Lobotes surinamensis, Malacoctenus n. sp., Megalops atlanticus, Mugil bananensis, Mugil capurrii, Negaprion brevirostris, Rhinecanthus aculeatus, Sardinella aurita, Sciaena umbra, Serranus heterurus, Sphyraena barracuda, Uranoscopus cadenati, and Zu cristatus are recorded for the first time from the Cape Verde Islands. We have recognized 77 previous records as identification errors or registration errors and indicate 35 other records as doubtful. Including the 24 new records, we now list 315 fish species from the coastal waters of the Cape Verde Islands. Twenty of them (6.3 %) appear to be endemic to the archipelago. Source

Fischer G.,University of Bremen | Karstensen J.,Leibniz Institute of Marine Science | Romero O.,University of Bremen | Donner B.,University of Bremen | And 8 more authors.
Biogeosciences | Year: 2016

Particle fluxes at the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic for the period December 2009 until May 2011 are discussed based on bathypelagic sediment trap time-series data collected at 1290 and 3439m water depth. The typically oligotrophic particle flux pattern with weak seasonality is modified by the appearance of a highly productive and low oxygen (minimum concentration below 2 μmol kg-1 at 40m depth) anticyclonic modewater eddy (ACME) in winter 2010. The eddy passage was accompanied by unusually high mass fluxes of up to 151 mgm-22 d-1, lasting from December 2009 to May 2010. Distinct biogenic silica (BSi) and organic carbon flux peaks of ∼15 and 13.3 mgm-2 d-1, respectively, were observed in February-March 2010 when the eddy approached the CVOO. The flux of the lithogenic component, mostly mineral dust, was well correlated with that of organic carbon, in particular in the deep trap samples, suggesting a tight coupling. The lithogenic ballasting obviously resulted in high particle settling rates and, thus, a fast transfer of epi-/mesopelagic signatures to the bathypelagic traps. We suspect that the two-to three-fold increase in particle fluxes with depth as well as the tight coupling of mineral dust and organic carbon in the deep trap samples might be explained by particle focusing processes within the deeper part of the eddy. Molar C :N ratios of organic matter during the ACME passage were around 18 and 25 for the upper and lower trap samples, respectively. This suggests that some productivity under nutrient (nitrate) limitation occurred in the euphotic zone of the eddy in the beginning of 2010 or that a local nitrogen recycling took place. The δ15N record showed a decrease from 5.21 to 3.11 from January to March 2010, while the organic carbon and nitrogen fluxes increased. The causes of enhanced sedimentation from the eddy in February/ March 2010 remain elusive, but nutrient depletion and/or an increased availability of dust as a ballast mineral for organic-rich aggregates might have contributed. Rapid remineralisation of sinking organic-rich particles could have contributed to oxygen depletion at shallow depth. Although the eddy formed in the West African coastal area in summer 2009, no indications of coastal flux signatures (e.g. from diatoms) were found in the sediment trap samples, confirming the assumption that the suboxia developed within the eddy en route. However, we could not detect biomarkers indicative of the presence of anammox (anaerobic ammonia oxidation) bacteria or green sulfur bacteria thriving in photic zone suboxia/hypoxia, i.e. ladderane fatty acids and isorenieratene derivatives, respectively. This could indicate that suboxic conditions in the eddy had recently developed and/or the respective bacterial stocks had not yet reached detection thresholds. Another explanation is that the fast-sinking organic-rich particles produced in the surface layer did not interact with bacteria from the suboxic zone below. Carbon-ate fluxes dropped from ∼52 to 21.4 mgm-2 d-1 from January to February 2010, respectively, mainly due to reduced contribution of shallow-dwelling planktonic foraminifera and pteropods. The deep-dwelling foraminifera Globorotalia menardii, however, showed a major flux peak in February 2010, most probably due to the suboxia/hypoxia. The low oxygen conditions forced at least some zooplankton to reduce diel vertical migration. Reduced "flux feeding" by zooplankton in the epipelagic could have contributed to the enhanced fluxes of organic materials to the bathypelagic traps during the eddy passage. Further studies are required on eddy-induced particle production and preservation processes and particle focusing. © 2016 Author(s). Source

Oliveira M.T.,Oceanario de Lisbon S.A | Oliveira M.T.,University of Algarve | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | And 3 more authors.
Journal of Applied Ichthyology | Year: 2015

Summary: This study reports weight-length and length-length relationships for selected coastal reef fish species of the Cape Verde Archipelago (tropical north-eastern Atlantic). Specimens were caught with different types of gear (long-lines, hand-lines, purse-seines and traps) during commercial fishing activities and sampled during fish market operations. A total of 8328 individuals were sampled, representing 29 species from 14 Families. This study provides the first references on weight-length and length-length relationships for five and 23 fish species worldwide, for 10 and 24 species for the Eastern Atlantic and for 12 and 26 species for Cape Verde Archipelago, respectively. Additionally, it provides revised weight-length relationships for 11 species from Cape Verde waters. © 2014 Blackwell Verlag GmbH. Source

Hauss H.,Leibniz Institute of Marine Science | Christiansen S.,Leibniz Institute of Marine Science | Schutte F.,Leibniz Institute of Marine Science | Kiko R.,Leibniz Institute of Marine Science | And 8 more authors.
Biogeosciences | Year: 2016

The eastern tropical North Atlantic (ETNA) features a mesopelagic oxygen minimum zone (OMZ) at approximately 300-600 m depth. Here, oxygen concentrations rarely fall below 40 μmol O2 kgg-1, but are expected to decline under future projections of global warming. The recent discovery of mesoscale eddies that harbour a shallow suboxic (< 5 μmol O2 kgg-1) OMZ just below the mixed layer could serve to identify zooplankton groups that may be negatively or positively affected by ongoing ocean deoxygenation. In spring 2014, a detailed survey of a suboxic anticyclonic modewater eddy (ACME) was carried out near the Cape Verde Ocean Observatory (CVOO), combining acoustic and optical profiling methods with stratified multinet hauls and hydrography. The multinet data revealed that the eddy was characterized by an approximately 1.5-fold increase in total area-integrated zooplankton abundance. At nighttime, when a large proportion of acoustic scatterers is ascending into the upper 150 m, a drastic reduction in mean volume backscattering (Sv) at 75 kHz (shipboard acoustic Doppler current profiler, ADCP) within the shallow OMZ of the eddy was evident compared to the nighttime distribution outside the eddy. Acoustic scatterers avoided the depth range between approximately 85 to 120 m, where oxygen concentrations were lower than approximately 20 μmol O2 kgg-1, indicating habitat compression to the oxygenated surface layer. This observation is confirmed by time series observations of a moored ADCP (upward looking, 300 kHz) during an ACME transit at the CVOO mooring in 2010. Nevertheless, part of the diurnal vertical migration (DVM) from the surface layer to the mesopelagic continued through the shallow OMZ. Based upon vertically stratified multinet hauls, Underwater Vision Profiler (UVP5) and ADCP data, four strategies followed by zooplankton in response to in response to the eddy OMZ have been identified: (i) shallow OMZ avoidance and compression at the surface (e.g. most calanoid copepods, euphausiids); (ii) migration to the shallow OMZ core during daytime, but paying O2 debt at the surface at nighttime (e.g. siphonophores, Oncaea spp., eucalanoid copepods); (iii) residing in the shallow OMZ day and night (e.g. ostracods, polychaetes); and (iv) DVM through the shallow OMZ from deeper oxygenated depths to the surface and back. For strategy (i), (ii) and (iv), compression of the habitable volume in the surface may increase prey-predator encounter rates, rendering zooplankton and micronekton more vulnerable to predation and potentially making the eddy surface a foraging hotspot for higher trophic levels. With respect to long-term effects of ocean deoxygenation, we expect avoidance of the mesopelagic OMZ to set in if oxygen levels decline below approximately 20 μmol O2 kgg-1. This may result in a positive feedback on the OMZ oxygen consumption rates, since zooplankton and micronekton respiration within the OMZ as well as active flux of dissolved and particulate organic matter into the OMZ will decline. © 2016 Author(s). Source

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