Deep-Sea Grenadiers and Climate Change
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Deep-sea Grenadiers and Climate Change Danielle Fabian, Applied Marine and Watershed Science M.S. California State University Monterey Bay Mentor: Ken Smith Summer 2017 ABSTRACT Oceans display physical variability “over a range of vertical, horizontal, and temporal scales,” (Brierley and Kingsford 2009) that influences factors such as larval dispersal, physiology, and nutrient availability (Lindegren et al. 2016). Such variability within all marine ecosystems is vulnerable to climate change. Changes in variability could ultimately lead to a loss of key prey species, which in turn could negatively impact remaining predators that not only play an important role within their ecosystems, but that are also deemed important in commercial fisheries (Brierley and Kingsford 2009). In order to predict and manage the consequences of increased greenhouse gasses (GHGs) and climate change, it is vital that we understand the interactions and feedbacks between marine systems and climate-related changes. Grenadiers are apex predators, playing an important role within their ecosystems; therefore, it is necessary to understand changes occurring over time in grenadier species abundance in order to protect the ecosystems they reside in. Many Grenadiers are benthopelagic; in which, the adult stages reside in the deep sea or on the seafloor, while the larvae are planktonic and reside in the upper water column (Allen et al. 2006). Larvae and juveniles are particularly susceptible to changes in ocean variability (Brierley and Kingsford 2009); therefore, monitoring changes occurring in all life stages of environmentally and economically important fish species with the change in climate and surface conditions is vital in order to protect and manage fisheries in the future. This paper focuses on the process of determining and altering my thesis project throughout the MBARI summer internship program, ultimately describing the finalized thesis plan that resulted as an outcome of multiple trials and error. The project focuses on studying correlations between changes in grenadier populations over time in relation to changes in climate and surface conditions. This study will involve conducting a time series benthic and midwater transect annotation to determine changes in grenadier abundance and size during a continuing 28-year time series at an abyssal station in the northeast Pacific (Sta. M). In addition existing NOAA databases will be examined to obtain grenadier abundance and size data for all life stages. The research question is the following: Does grenadier population structure change in relation to climate variables? Grenadier abundance data will be compared to physical variables relating to climate and surface ocean conditions. Cross correlation analyses will be used to determine relationships between changes in fish populations, at Station M and along the California coast, and changes in climate and surface conditions over time. INTRODUCTION Climate Change Affecting Physical Variability and Fisheries: Since the mid-1800s, there has been a tremendous increase in carbon dioxide (CO2) in the atmosphere due to the combustion of fossil fuels on a global scale. This rise in CO2 has the potential to aggravate the greenhouse gas effect; an event that consists of CO2 and other gases trapping solar heat within the atmosphere, warming the planet (Recent Global Warming 2002). Additional effects of the rise of anthropogenic greenhouse gases include: rising sea levels, rising global mean sea-surface temperatures (SST), increased ocean acidity, perturbed regional weather patterns, altered ocean circulation, changes in the extent of oxygen-deficient dead-zones, and changed nutrient loads (Brierley and Kingsford 2009). Marine biological processes are affected by such physical consequences, which could ultimately impact ecosystem services and threaten human food security (Brierley and Kingsford 2009). In order to predict and manage the consequences of increased greenhouse gasses (GHGs) and climate change, it is vital that we understand the interactions and feedbacks between marine systems and climate-related changes. Oceans display physical variability “over a range of vertical, horizontal, and temporal scales,” (Brierley and Kingsford 2009) that influences larval dispersal, physiology, nutrient availability, species migration, production, and biodiversity (Lindegren et al. 2016). Such variability among and within all marine ecosystems is vulnerable to climate change. The condition of larvae and juveniles, as well as the timing of reproduction and reproductive output, can be affected by variability as well (Brierley and Kingsford 2009). Particularly susceptible to changes in salinity, temperature, and pH, juveniles and larvae may not have the ability to survive elevated temperatures that their adult stages are capable of surviving. Similarly, if the hatching time of larval eggs does not coincide with food availability, survival rates may be affected. Changes in food availability could stem from temperature-driven phenological changes that could alter the timings of plankton blooms; ultimately leading to “breaks in the food chains and wholesale departures of prey species” (Brierley and Kingsford 2009). The loss of key prey species could negatively impact remaining predators that not only play an important role within their ecosystems, but that are also deemed important in commercial fisheries (Brierley and Kingsford 2009). Grenadier and Focal Species: Grenadiers, of the family Macrouridae, are the most common benthic fish in the deep sea. The Macrourids generally have low recovery rates, and species that are commercially exploited may be overfished, resulting in a fishery collapse within a short time period (Large et al. 2003). In addition to being the most common benthic fish of the deep sea, grenadiers are important apex predators making it critical to understand changes in population structure over time. Many grenadiers, including the four focal species of this research project, are benthopelagic. The adult stages reside in the deep sea or on the seafloor, while the larvae are planktonic and reside in the upper water column (Allen et al. 2006). The following are brief descriptions of the grenadier focal species included within this project: Coryphaenoides acrolepis: C. acrolepis is a benthopelagic mid-slope grenadier species that is significantly more abundant than any other slope species (Cohen et al. 1990). This species is a target species in commercial fisheries. It is a non-migratory species that resides in the North Pacific at a depth range of 400- 1800 meters (Cohen et al. 1990). Due to its economic importance, it is necessary to monitor potential changes in abundance of this species over time to avoid over fishing. Coryphaenoides armatus: C. armatus is a deep-slope upper continental rise grenadier species found in all the world’s oceans, at depths between 800 and 4,000 meters (Cohen et al. 1990). This species is known to grow slowly; potentially living up to 75 years of age. Abundance of C. armatus is likely driven by migration in response to variation in food availability (Drazen et al. 2012; Bailey et al. 2006). C. armatus, although of no interest to fisheries, is often caught as by-catch and is difficult to differentiate from C. acrolepis. Coryphaenoides yaquinae: C. yaquinae is a rough abyssal grenadier species that dominates and is confined to the abyssal plains encompassed within the Pacific Ocean (Jamieson et al. 2012). Although preferring deeper depths, the species is known to inhabit a depth range of 3400 to 5800 meters (Wilson and Waples 1983). C. yaquinae is closely related to C. armatus, and the two species are almost indistinguishable from one another based on physical characteristics alone (Jamieson et al. 2012). While generally bathymetrically segregated, the two species co-exist on the Pacific continental margin between the 3400-4300 meter depth ranges (Jamieson et al. 2012). Coryphaenoides leptolepis: C. leptolepis is commonly referred to as the “Ghostly Grenadier”, and is listed as Least Concern because the species has no known predators and resides outside the range of fisheries. It is a bathydemersal species, inhabiting a depth range of 610-4000 meters, and can grow to 62 centimeters in length. C. leptolepis is native to the northeast and eastern central Pacific, as well as the western central, eastern central, northwest, and northeast Atlantic. Due to a lack of commercial importance and depth range, very little is known about C. leptolepis (Iwamoto 2015). For my internship this summer, the goal was to establish a thesis project for my Master’s at CSU Monterey Bay. While I originally thought that this would be a relatively straight-forward process, many road blocks occurred forcing several changes to my project through the internship. That being said, this paper elaborates on the evolving process of selecting my final project and not on the data ultimately required for a research paper. METHODS Attempt #1: C. acrolepis and C. armatus Study Both C. acrolepis and C. armatus are known to have pelagic larvae, which is ultimately the intermediate tie between the surface and the seafloor in determining what is happening between species. Changes is surface water conditions are probably affecting these species, and such species changes could ultimately affect fisheries. Aside from their larvae being at risk due to changes in physical variability within the oceans, the adults may also be at risk from fishing. Fishing effort is going deeper