Ocean Sense Community-Based Observatory Education Program

Teachers’ Guide

Welcome to Ocean Sense! Ocean Sense uses data and resources from the Community-Based Observatories, hosted by Ocean Networks Canada (ONC). This program provides a phenomenal

platform to “dive into” the ocean and explore the world beneath the waves. Instruments mounted on each observatory help scientists extend their senses and understand ocean processes by acting like their ears and eyes in the sea.

1. Program Introduction

1.1 Vision “Local observations, global connections” Through the Ocean Sense program we hope to inspire the next generation of ocean stewards. Through the use of Ocean Networks Canada’s Community-Based Observatories students will gain knowledge of their local marine environments. By connecting with other students via social media and face-to-face events and by engaging in educational resources, students will also gain a global perspective of ocean processes.

1.2 Pillars of the Program “Ocean, Technology, Community” In this program, the associated learning objectives will create the base for the project and the core educational resources provided by ONC. Furthermore, the pillars will provide educators with an outline from which to incorporate this project into the classroom.

The Ocean 1. An interdisciplinary approach is needed to understand the ocean. a. Core educational resources include content from marine biology, chemistry, physics, geology, engineering and the social sciences. 2. The global ocean is interconnected. a. Core educational resources will explain the relationship between ocean processes such as ocean currents, nutrient distribution, and food web dynamics.

The Technology 1. Exploration and discovery of the ocean is enabled through technology. a. Core documents will include instrument details so as to understand how technology informs science. b. Keystone activities include detailed introductions to instruments so educators understand the tools used in this program. 2. Technology enables long-term study and investigations over time.

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a. Students and educators can use observatory data to gain a better understanding of their local environment. b. Students and educators can use observatory data to gain a better understanding of ocean processes year after year through long-term data collection.

The Community 1. Personal connections between students and their local environment will ignite the understanding that humans and the ocean are interconnected. a. Core educational resources will include references to how humans use and impact the ocean. 2. Connections between schools will encourage students’ understanding of local oceans to broaden to a global perspective. a. Creating a network of students and teachers involved with the community-based observatory project will allow understanding of other ocean regions and global issues. b. Facilitating interaction between students and educators through online discussion and face-to-face events. 3. Connections between schools will inspire partnerships and scientific collaboration, through: a. Sharing of data via reports, social media, presentations, and events.

1.3 How to Use the Resources This resource is intended to be used by teachers at any point in the curriculum, over the course of a full year. Every instrument collects data continually, so you are strongly encouraged to revisit the data often. As seasonal trends appear over time in the data, you may gain a very different perspective of the seas around you. As data become available, you may find the outcome of a particular lesson plan is different that when you first explored it (in a good way).

Think of the Ocean Sense program as a bicycle and these lessons are training wheels. We encourage you to ask questions and explore your data with a sense of ownership. The questions you choose to explore and discover may be the first of their kind. Encourage your students to engage and explore in this resource as often and as freely as they can. Some of the greatest discoveries and clearest answers were only found because people had the time to stop and look.

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Don’t forget, you’re not alone in exploring with these resources: connect with other users and explore questions via social media. Also, please don’t hesitate to contact the ONC Learning Team with questions and feedback. We want to know what questions you explore, and what discoveries you make.

2. Who is Ocean Networks Canada? Ocean Networks Canada, an initiative of the University of Victoria, operates the world-leading NEPTUNE and VENUS cabled ocean observatories for the advancement of science and the benefit of Canada. These observatories support transformative coastal to deep ocean research and technology. It enables real-time interactive experiments, focused on ocean health, ecosystems, resources, natural hazards, climate change and marine conservation.

In addition to the larger observatories, Ocean Networks Canada has also begun operating smaller platforms known as community-based observatories. Currently two community-based observatories exist: one in Cambridge Bay, Nunavut, and the other in Mill Bay, BC.

The observatories collect continuous, real-time measurements of temperature, salinity, oxygen, density, pressure, carbon dioxide, video footage, hydrophone recordings, and many other properties. Data is considered real-time because it is streamed online within seconds of being collected, allowing researchers, educators, students, and the general public the opportunity to analyze changes in ocean properties first-hand from the comfort of their labs, classrooms, or homes.

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Figure 1. Locations of Ocean Networks Canada’s cabled underwater observatories.

NEPTUNE (Northeast Pacific) VENUS (Salish Sea)

Depths: 23–2660 m. Depths: surface–300 m

• Situated off the west coast of • Situated between Vancouver Vancouver Island, extending Island and the Mainland in the 300 km offshore, down the Strait of Georgia and Saanich continental slope and across Inlet. the Juan De Fuca tectonic • 44 km array of fibre optic plate. cables. • 850 km loop of fibre optic • 4 operational nodes. cables. • Coastal radars. • 5 operational nodes. • Underwater gliders. • Remotely Operated Robot: • Instruments mounted on Wally. ferries. • Vertical Profiling System (VPS). • Buoy Profiling System (BPS).

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What are ONC’s major science themes? • Understanding Human-Induced Change in the Ocean. • Life in the Coastal and Deep-Sea. • Interconnections Amongst the Seafloor, Ocean, and Atmosphere. • Seafloor and Sediment in Motion.

Benefits of real-time data from the deep-sea: • Increased scientific knowledge of the marine ecosystem and its processes. • Increased understanding of human impacts. • Natural hazard detection and warning for coastal communities. • Education opportunities.

Inspiring the Next Generation Integrated with the extraordinary science and incredible innovations coming from Ocean Networks Canada, is the Learning Team, which is dedicated to bringing ONC’s science, technology, and knowledge to students and educators across the country. Using real-time data, the Learning Team creates authentic and engaging learning experiences that encourage the integration of marine science into the classroom.

Educators can further engage with ONC through: • Requesting classroom presentations. • Attending (or requesting) workshops. • Downloading learning resources. • Incorporating real-time data (video, audio, point source data) from our observatories into the classroom. • Using our Citizen Science Tools such as Digital Fishers and iBooks such as the Marine Field Guide. • Following our Twitter feeds (@Ocean_Learning) and Facebook channels. • Virtually joining in on our research expeditions.

3. Data Access

3.1 Site-Specific Data Pages As part of the Ocean Sense webpages, we have created specific community-based observatory data pages that provide the following information: • Latest data readings.

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• Interactive plotting tools, where students can choose the variable and date range to graph. • The latest video clips. • The latest hydrophone recording. • A “state of the ocean” plot which shows seasonal and annual trends.

The site-specific data pages allow students to view, create plots, and save data coming from the observatories. The site-specific data pages are meant to be a one- stop-shop and allow for easy navigation to the data and intuitive data analysis.

While data plots can be constructed for any time range, the video section will only show the last video recorded when the lights were on. In order to view archived video data, students will have to access ONC’s Oceans 2.0 online data tools.

3.2 Oceans 2.0 Oceanographic data collected by Ocean Networks Canada (ONC) are available on the Internet using Oceans 2.0 web tools. These tools provide access to general information about instruments and associated technology and allow users to view, search, and download archived data.

To begin accessing ONC data from Oceans 2.0, please visit http://www.oceannetworks.ca and click on the “Data & Tools” tab to view the tools that are currently available for each network. Selecting a tool will bring you to the Oceans 2.0 login/registration page.

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Figure 2. Oceans 2.0 login/registration page.

You will need to create a username and password: this can be done for an entire class to share or students can create individual accounts.

Please note: ONC respects your privacy. By signing up for an account you will not be spammed and your email and password will remain secure. If interested you can also click to receive our monthly newsletter while creating an account.

Currently, Oceans 2.0 only permits access to data and instruments from one particular observatory at a time. Click the “Tools” tab and select “Network Preference” to select a network (e.g. Arctic Observatory or Brentwood College) in Oceans 2.0. Once you have selected a network, all of the tools within Oceans 2.0 will be coordinated to that observatory.

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Figure 3. Selecting an observatory network from the dropdown menu.

3.2.1 Plotting Utility Plotting Utility is the main scalar data visualization tool. It facilitates comparisons and visual correlations by plotting data from multiple sensors. Users can build their own graphs and customize various aspects of the plot such as colour and graph type, to make each one look unique.

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Figure 4. Data Plotting Utility front page.

NOTE: The data-specific pages on the Ocean Sense webpages are simplified versions of this tool. You should not need to access the Plotting Utility unless you wish to explore the data of ONC’s larger observatories, NEPTUNE and VENUS.

3.2.2 SeaTube Pro SeaTube Pro is a video viewer and annotation interface for deep-sea videos collected by the undersea observatories, remotely operated vehicles during maintenance cruises, and for time-lapse videos collected by shore cameras. SeaTube Pro allows the user to watch, search, and create video playlists for specific purposes.

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Figure 5. SeaTube Pro front page.

NOTE: Although the Ocean Sense webpages do have the latest video recordings, if you wish to access archived video, you will need to access SeaTube Pro.

3.2.3 Digital Fishers The Digital Fishers citizen science project, developed in collaboration with UVic’s Centre for Global Studies (CfGS), encourages scientists, students, and the public to make observations and comment on large volumes of scientific data. The Digital Fishers tool works by applying the principle of “crowdsourcing”. This crowdsourcing project invites a large number of individuals, including non-specialists, to use the Internet-based platform, make observations, annotations, and verifications of data gathered from underwater video.

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Figure 6. Digital Fishers interface.

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4. Oceanographic Terms and Concepts This section contains a brief overview of some of the terms, instruments and concepts you may encounter while using the Community-Based Observatories, hosted by Ocean Networks Canada.

4.1 Ocean Properties

4.1.1 Salinity Refers to the concentration of dissolved salts in seawater and can be (and was traditionally) defined as the total weight (in grams) of inorganic salts dissolved in 1 kg of seawater. Since measuring the weight of salinity is a tedious task, a salinometer is commonly used to determine the salinity of seawater instead. A salinometer measures the electrical conductivity of water, which increases proportionally with increasing salt content. Both sodium and chloride ions are the predominating constituents of salt content; however, several other inorganic salts including sulphate, magnesium, and potassium contribute to the salinity of seawater.

Surface salinity values are usually provided in Practical Salinity Units (PSU) based on an internationally agreed upon standard solution value. In the open ocean, salinity generally ranges from 32–37 PSU with an average salinity of 35 PSU, and is influenced by global climate. Salinity is increased through evaporation, and is decreased by the addition of freshwater as rain or river inflow. Within enclosed seas such as the Red Sea, high evaporation rates produce salinity values around 40 PSU, whereas seas with high river inflow such as the Baltic Sea have surface salinity values around 7 PSU. Salinity rapidly changes with depth within an area known as the halocline. Below the halocline at a depth of about 1000 m, salinity is 34.5–35.0 PSU at all latitudes (Lalli and Parsons, 2010).

4.1.2 Temperature Water temperature is very important as it strongly influences many physical, biological, chemical, and geochemical events. A continual exchange of heat and water between the ocean and the atmosphere establishes sea surface temperature. Because solar radiation intensity varies with latitude, sea surface temperatures range from temperatures exceeding 30° C in the tropical oceans to temperatures as low as -1.9° C in the polar oceans.

Turbulent mixing produced by winds and waves transfers heat downward from the

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surface and can create a mixed surface layer with uniform temperature. Below the mixed layer, water temperature begins to rapidly decline with depth. This area within the water column is known as the thermocline and generally occurs between 200–1000 m. Apart from hydrothermal vents, water temperatures never rise above 4° C below the thermocline (2000–3000 m), regardless of latitude (Lalli and Parsons, 2010).

4.1.3 Density The density of an object or solution refers to its mass per unit volume and is measured in kilograms per cubic metre (kg/m3). Solutions of varying densities will arrange themselves in order of increasing density from the surface down. Similarly, objects that are less dense than the surrounding solution are positively buoyant and will float. In the ocean, the primary determinants of density of seawater are temperature, salinity, and pressure. As temperature decreases and salinity and pressure increases, seawater density will increase accordingly (Lalli and Parsons, 2010).

4.1.4 Pressure Measured as the force per unit area exerted perpendicular to the surface of an object, pressure is often expressed as kilopascals or decibars (Talley et al, 2011). In the ocean, pressure is measured by instruments such as conductivity-temperature- depth (CTD) sensors or bottom pressure recorders (BPRs), which measure the weight of the overlying water column. Measuring ocean depth provides an estimate of the pressure (1 metre is equivalent to 1 decibar). Pressure measurements are also used to view daily tidal cycles. During high tide, the water column height above the BPR increases and a greater pressure is exerted onto the recorder, leading to a larger reading. During low tide, the water column height decreases, and a smaller pressure is recorded.

4.1.5 Oxygen Sea surface water is saturated with oxygen from a continual gas exchange across the atmosphere–ocean interface. Oxygen production by phytoplankton also increases oxygen saturation in surface waters. Ocean oxygen concentrations are commonly measured in millilitres per litre (ml/l). The vast majority of marine life depends upon oxygen to survive. Oxygen is consumed both by respiring organisms and by the bacterial oxidation of organic detritus; this causes the oxygen saturation below surface layers to gradually decrease with depth.

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4.1.6 Chlorophyll Phytoplankton have photosynthetic pigments which convert solar energy into chemical energy through the process of photosynthesis. The most abundant photosynthetic pigment produced is chlorophyll. Since phytoplankton depend upon sunlight to grow, chlorophyll concentrations rapidly decrease with depth in the ocean. Chlorophyll concentrations (µg/l) are measured with a fluorometer and are often used to approximate the level of primary production. The amount of primary production present provides oceanographers with important information as to how much energy is available for animals further up the marine food chain (Lalli and Parsons, 2010).

4.2 Ocean Technology

4.2.1 Secchi Disk Created in 1865 by Pietro Angelo Secchi, the Secchi disk is a circular disk separated into black and white quadrants. It is used to gauge water clarity (or turbidity) by measuring the depth at which it is no longer visible from the surface.

4.2.2 CTD A CTD is used to measure the Conductivity (S/m), Temperature (oC), and Depth (m) in the water. A CTD can be deployed in a fixed location on an observatory (e.g. VENUS and NEPTUNE underwater cabled observatories), or it can be lowered over the side of a ship to collect a continuous profile of the water properties through the water column. The sensors in the instrument actually measure conductivity, temperature and depth, which can be used to derive salinity, pressure, density, and sound speed. CTDs are used to characterize basic water properties and are fundamental in a wide range of oceanographic research areas. Additionally, CTDs can be equipped with an oxygen sensor to detect the oxygen concentration of seawater.

4.2.3 Hydrophone An underwater microphone used to detect and record ambient sound in the ocean. Using hydrophones, scientists study marine mammal vocalizations, noise pollution such as that caused by shipping traffic, and seismic activity.

4.2.4 Echo-sounder Acoustic signals emitted by an echo-sounder reflect (echo) off of biomatter and bubbles in the water column and then propagate back to the instrument, where they are measured and recorded. For example one type of echo-sounder is the

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Zooplankton Acoustic Profiler (ZAP), which produces an image using recorded acoustic backscatter to assess how the vertical distribution of zooplankton and fish vary over time.

4.2.5 Fluorometer Used to identify the presence and amount of chlorophyll in seawater. A fluorometer detects electromagnetic waves (e.g. light), which at depth is usually a measure of the fluorescence of a substance. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.

4.2.6 Acoustic Doppler Current Profiler (ADCP) Measures water current velocities (speed and direction) using the Doppler effect of sound waves scattered back from particles within the water column. ADCPs can either be permanently deployed on the ocean seafloor, or deployed on a moving ship. Backscatter data from ADCPs can also be analyzed to provide information about fish, plankton, and bubbles in the water column.

4.2.7 Video Camera An underwater video camera system consists of a network video camera, typically mounted on a pan and tilt mechanism, with lights and lasers for estimating the size of objects in the field of view. Video data is used by biologists to study organisms including their diversity, distribution, feeding, and behaviour. Other visual aspects of the deep sea such as geological features and environmental changes can also be observed in video.

4.2.8 Sonar Sound travels better through water than radar or light, so it is often used to determine where objects are underwater. The instrument emits a signal or pulse of sound and if an object is in the way of the sound, some of the sound will hit the object, bounce off it, and return to the sonar device. The instrument then uses this information to determine where the object is the water and create a ‘sound map’ of the area. In nature, sonar is called ‘echolocation’.

4.2.9 Bottom Pressure Recorder (BPR) This instrument measures the pressure of the water column sitting above it and is sensitive enough to predict millimetre changes in water level. The instrument can be used to measure the increase in water during tidal activity, and can also be used to detect tsunamis. When a tsunami passes over a bottom pressure sensor, the instrument detects that the water pressure above it is significantly greater than

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normal, and can alert researchers to the anomaly.

4.2.10 Seismometers A seismometer measures the movement of the earth. Seismometers work on the principle of inertia. A small mass of metal within a coil inside the seismometer doesn’t move until a ground shaking acts upon it. When the earth moves, it moves the seismometer and the metal mass generates a current in the coil which is then recorded. Very sensitive seismometers can even detect movements smaller than a millimetre.

4.2.11 Turbidity Sensors Turbidity (NTU) is a measure of how much particulate matter is suspended in water. A water sample with a high turbidity has large amounts of particles in the water, which can make it difficult to see through. Water with low turbidity has a small amount of particles in the water and looks clear or nearly clear. Turbidity can be used to determine water conditions which can be used to monitor the health of an area. For example an area with lots of plankton growth has a lot of nutrients and a lot of turbidity. And area with minimal nutrients and not a lot of plankton growth would have a low turbidity. Also, underwater landslides generate a lot of turbidity and sediment plumes from river deltas can be seen with turbidity sensors, too.

4.2.12 Sediment Traps Used to collect samples of falling marine particles, sediment traps are like rain gauges for oceanic materials. The instrument is placed on the sea floor with the open end pointed to the surface. As marine materials (nutrients, dead plankton, dead animals and plants) sink to the bottom, they become ‘marine snow’. These particles are collected in sediment traps and studied by scientists.

4.3 Ocean Ecosystems The ocean supports a great diversity of ecosystems spanning from the deep sea to the shallow intertidal zone. Community composition and species richness vary widely.

4.3.1 Deep Sea The deep-sea environment includes a wide range of depths identified as the bathypelagic (1000–4000 m), abyssopelagic (4000–6000 m) and hadalpelagic (6000– 11000 m) zones. At these depths, seafloor environments are relatively stable and homogenous with respect to both physical and chemical parameters compared to the shallow waters. Water temperatures remain quite low (-1–4 °C) and salinity

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values average around 35 PSU. The seafloor consists primarily of soft bottom sediments and clays, originating from both land and the sinking of dead planktonic organisms.

Marine organisms occupying deep-sea environments must endure low temperatures, darkness, and high pressures. Organisms acquire nutrients primarily from marine snow: a shower of organic detritus from the photic zone. Consequently, life in the deep sea is highly dependent upon surface primary production as a food source, even though only a small percentage (~1–5%) of the phytoplankton produced in the euphotic zone are transferred to the ocean bottom. Food limitation in the deep sea is the primary reason why population densities and biomass are much less than shallow water areas (0–200 m).

Unlike species abundance, species diversity increases with depth from about 200– 2500 m. The wide range of organisms observed at these depths includes small crustaceans, Molluscs (snails and clams), Cnidaria (sea anemones and sea pens), primitive crinoids (stalked sea-lilies) and other echinoderms (sea stars and sea- cucumbers). Deposit-feeding infaunal organisms generally dominate over other organisms in the deep sea because of the abundance of soft organic-rich sediments on the seafloor. Organisms that feed on suspended particles are much less abundant in the deep sea and are usually restricted to particular localities. This is because most of these organisms (i.e. sea anemones and barnacles) require hard substrates to which to attach and high concentrations of suspended food particles (Lalli and Parsons, 2010).

4.3.2 Hydrothermal Vents Hydrothermal vents form along ocean spreading centres and back-arc basins where seawater percolates through the thin ocean crust to form hydrothermal fluid. Seawater becomes enriched in sulphur and dissolved minerals (e.g., iron, zinc, and copper) through reactions with superheated rock within fractures and permeable zones in the seafloor near the magma chamber, and is released as superheated (250–400 °C) buoyant plumes of hydrothermal fluid. Once the vent effluent mixes with the cold seawater, minerals precipitate and form black metal sulphide deposits and tall chimneys. When the seawater does not penetrate deep enough into the ocean crust, chemical reactions are partial and the fluid is released as diffuse flow characterized by lower temperatures (20–50 °C). The mixing of hydrothermal fluid with seawater generates steep heat and chemical gradients, sometimes at the scale of a few centimetres.

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Vents are home to an endemic faunal community independent of energy from sunlight and photosynthetic organisms. The vent food web fully relies on chemical fluxes as a source of energy, through a process known as chemosynthesis. Vent organisms including limpets and snails graze upon dense mats of sulphur oxidizing bacteria, whereas tubeworms obtain nutrients is through symbiosis with sulphur oxidizing bacteria that live in their gut (trophosome).

4.4 Ocean Threats

4.4.1 Ocean Acidification

Concentrations of anthropogenic carbon dioxide (CO2) in the Earth’s atmosphere have been rising at a rapid rate from human fossil fuel consumption (Guinotte and

Fabry, 2008). An increase in atmospheric CO2 leads to a rise in oceanic CO2 levels through continual air-sea gas exchange. When CO2 dissolves in the ocean it decreases the pH (increase the acidity) of the water and reacts with seawater and carbonate, leading to a decrease in the amount of available carbonate in the ocean (Emerson and Hedges, 2008).

A decline in the available carbonate ions means that calcifying organisms must expend significantly more energy to build and maintain their hard shells. This will have a direct impact on the marine organisms which build shells composed of either biogenic calcium carbonate or aragonite. These organisms include tropical and cold water corals, molluscs (clams and mussels), echinoderms (sea stars), phytoplankton (foraminifera and coccolithophores), zooplankton (pteropods), and coralline algae. In return, the decline of calcifying organisms can have a substantial impact on the marine ecosystem. Many calcifying organisms are an important source of nutrition and shelter for higher-trophic level organisms (Guinotte and Fabry, 2008).

4.4.2 Hypoxia Low oxygen environments (hypoxic zones) are increasing throughout marine coastal ecosystems on a global scale (Diaz and Rosenberg, 2008). Hypoxic zones occur when oxygen levels fall under 1.5 ml/l, resulting in an environment where only a limited number of adapted species can thrive (Ocean Properties, 2013). Marine hypoxia can occur either naturally in deep basins, fjords, and upwelling regions, or through anthropogenic disturbances. The main factors responsible for increasing hypoxic environments are eutrophication and climate change.

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Eutrophication occurs when an excess of nutrients enters into the ocean either by natural or anthropogenic processes (e.g., industrial activities or mining practices) (Diaz and Rosenberg, 2008). The nutrient excess triggers massive phytoplankton blooms. When phytoplankton cells die, the high level of organic matter is decomposed by bacteria, a process which exhausts the oxygen supply (Ocean Properties, 2013).

Climate change increases sea surface temperatures, leading to reduced oxygen solubility and increased water stratification. When the water column is stratified, oxygen saturated surface waters no longer recharge bottom waters at a sufficient rate, leading to hypoxic conditions.

Ocean hypoxia can pose harmful effects on the growth, survival, reproduction, and behaviour of many marine species. Compared to other coastal and deep-sea environments, biodiversity is lower in hypoxic regions (e.g. Matabos et al., 2012).

A number of coastal zones around the world are significantly impacted by hypoxic conditions. Saanich Inlet, located on the southeastern side of Vancouver Island is affected by ocean hypoxia. Saanich Inlet is a naturally occurring hypoxic estuarine fjord due to high productivity and the presence of a shallow sill located at the mouth of the inlet. This sill restricts movement of neighbouring oxygen-rich waters into the deep basin (Manning et al., 2010).

4.4.3 Coral Bleaching Bleaching occurs when stress causes corals to expel symbiotic algae (zooanxthelle) resulting in a loss of colour (hence the appearance of being bleached). Several factors can cause bleaching, many tied to climate change, including: seawater warming, ocean acidification, sea-level rise, or changes in storm intensity. However, the biggest driver resulting in mass bleaching events is warming temperatures. By 2080, 80–100% of the world's coral reefs will suffer annual bleaching events due to global warming.

4.4.4 Habitat loss Habitat loss results in the destruction of ecological structures and functions vital to maintaining the richness and abundance of species native to an area. While habitat loss can be caused by natural hazards such as lightning strikes or avalanches, the human-caused (anthropogenic) loss of habitat is of greatest concern. Activities include bottom trawling, crude oil spills, pollution and industrial, urban and

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agricultural development. These activities are incredibly destructive to a variety of marine environments, particularly estuaries, swamps, marshes, and wetlands, which serve as breeding grounds or nurseries for nearly all marine species (Lalli and Parsons, 2010).

4.4.5 Eutrophication Eutrophication is the release of excess nutrients (primarily nitrogen and phosphorus) into a waterway arising from human activities (industry, mining, farming, storm drains, etc.). Excess nutrients promote increase algal growth, sometimes resulting in massive and lethal "blooms."

4.4.6 Overfishing Arguably the most serious and detrimental human impact on marine ecosystems, fishing removes more than 100 million tonnes of fish and shellfish every year. Large fishing vessels are now equipped with thousands of baited long lines and mid- water trawl nets with a mouth gape of 130 m and length of 1 km. These advances in fishing technology have made it easier to catch significantly more fish in a smaller amount of time, negatively impacting the species composition of both pelagic and benthic communities.

Commercial fisheries discard about one of every four animals caught, although the percentage of by-catch is likely much larger because the majority of it goes unreported. Fisheries discard species which have limited economic value or are too small. In particular, shrimp fisheries in the Gulf of Mexico catch and discard at least 5 million juvenile red snapper annually. Unfortunately, the majority of by-catch species are unable to survive after they have been released (Lalli and Parsons, 2010).

4.5 Glossary References Diaz R., and Rosenberg R. (2008). Spreading dead zones and consequences for ecosystems. Science: 321(5891), 926–929.

Emersen, S.R., and Hedges, J.I. (2008). Chemical Oceanography and the Marine Carbon Cycle. New York, USA: Cambridge University Press.

Guinotte, J. M., and Fabry, V. J. (2008). Ocean acidification and its potential effects on marine ecosystems. Annals of the New York Academy of Sciences: 1134, 320– 342. DOI:10.1196/annals.1439.013

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Lalli, C. M., and Parsons, T. R. (2010). Biological Oceanography: An Introduction. (2nd ed.). Burlington, MA: Elsevier Ltd.

Manning, C., Hamme, R.C., and Bourbonnais, A. (2010). Impacts of deep-water renewal events on fixed nitrogen loss from seasonally-anoxic Saanich Inlet. Marine Chemistry: 122(1-4), 1–10.

Matabos M., Tunnicliffe V., Juniper S.K., and Dean C. (2012). A year in hypoxia: epibenthic community responses to severe oxygen deficit at a subsea observatory in a coastal inlet. PLoS ONE: 7(9):e45626. DOI:10.1371/journal.pone.0045626

Ocean Properties. (2013). Retrieved March 24. 2013, from http://venus.uvic.ca/research/ocean-properties/.

Talley, L., Pickard, G. L., Swift, J., and Emery, W. J. (2011). Descriptive Physical Oceanography: An Introduction. (6th ed.). Burlington, MA: Butterworth-Heinemann.