in this video I want to continue talking about the importance of community interactions of species interactions in communities another way of saying this trophic interactions and the implications that trophic interactions have for entire ecosystems I also want to talk a little bit more about keystone species introduce the concept of foundation species and I want to do all of this using another example ecosystem which is the coral reef ecosystem and coral reefs are a really important system for us to spend a little bit of time on in this class because they are incredibly important in the ocean as a whole and they're also incredibly threatened so in the 1970s a survey of the coral reef systems globally showed that more than 50% of coral reefs had live coral growth on them in any subsequent survey in 2012 only 8% of coral reef ecosystems around the world showed live coral growth so that's a really troubling statistic that's a really troubling finding and we also know and you probably have heard about this that we continue to have every year new bleaching events coral bleaching events globally and I'll explain what coral bleaching is in this video if you don't know what that is already and so why are why are we worried about coral reefs disappearing well coral we first of all there there are like I'm trying to remember the number I think something like 800 different species of reef building corals and so when I talk about coral reefs I'm referring to coral reefs that are made up of all of these different species of reef building coral corals and coral reef ecosystems support lots of other life in fact it's been estimated that the coral reef ecosystems in the world's oceans supports up to 50 percent of the biodiversity of the ocean and so that doesn't mean directly it doesn't mean all the time but either species that live in coral reef ecosystems or species that use coral reef ecosystems for feeding grounds or for nurseries or for refuge for some purpose throughout their lifecycle many many species use coral reef ecosystems and it's because of this that some people consider coral reefs to be I should say coral the coral species in coral reef ecosystems to be keystone species well this is a little different than the types of keystone species we've looked at before right the in the past we've looked at keystone species that are top predators and that's typically what we tend to see with keystone species but in the coral reef ecosystem the reason that some people call corals keystone species is because remember the definition of keystone species the definition is that it's a species that has a significant impact in the ecosystem to which it belongs and that it is in relatively low abundance proportionate to the impact that it has so the abundance of this species in the ecosystem is disproportionate with how important it is in the ecosystem so this is a little this is a little it takes a little bit of a different perspective to imagine how coral reefs are in relatively low abundance because if you think of what you picture is a coral reef system and I have a couple of pictures here right this is a coral reef ecosystem this is another one we have long here on the top left oh right there's a lot of different types of coral there they're also fish and all sorts of other organisms but there's a lot of coral and so it seems relatively abundant right but the way that people justify or I should say define coral as a keystone species is that they look at the entire oceans on the planet and they say that the amount of space the amount of volume that coral takes up in the ocean is disproportionate to them to be percentage of biodiversity that are supported that is supported by coral reefs and so it's said that coral takes up less than less than point zero one five percent of the ocean the space of the ocean and supports up to 50 percent of the biodiversity of the ocean so that's how we define coral reef says as reef building corals as keystone species and so what are some of the threats to coral reefs well some of the threats are certain fisheries practices but again we talked about this with urgence that will dredge the bottom of the ocean and rip up coral reefs in their path and also a direct collection by human so we you know divers and people will just go and collect coral so don't buy coral souvenirs don't support that industry it's a direct collection by humans fisheries practices pollution in lots of different forms ocean acidification being one form of pollution and and so it does one other threat I want to tell you about but as if that's not enough hmm and hmm feel like I'm forgetting something okay so keystone species we talked about how coral the keystone species the next thing that I wanted to share with you is a important symbiotic relationship so speedy OSIS is something that you learned about for this module that you first read about it and then we've talked about it a couple of times now coral reef building corals have an important critical symbiotic relationship with microscopic algae called zooxanthellae and I've spelled it here for you because everyone I know says it differently I'm going to say those anthalie but these are microscopic algae that lives inside of coral and the symbiotic relationship that coral and those ansel a have with one another is a mutualistic relationship as a mutualism it's a mutualism because the zooxanthellae receives protection in terms of they can they live inside the coral so they have refuge there they also receive important materials for photosynthesis they are photosynthetic algae they receive important materials for photosynthesis from the coral and in fact those materials come from the corals waste products so it's a really interesting efficient system so they received important nutrients or not nutrients materials for the production of food they received protection and then the coral receives nutrients from the zooxanthellae so that those anthalie are photosynthetic and the coral actually rely on the zooxanthellae most species of coral rely on the NAM but they received lots of nutrients from those anthalie they also receive the removal of waste products from zooxanthellae so they don't have waste products build up because the zooxanthellae take those waste products and use them so those are just a couple of examples of the benefits that each species receives from their mutualism okay so this brings us to to the concept of coral bleaching oh and that's why I have this this photo in the middle here so this is bleached coral this is white coral right so when you see pictures of white coral or when you see coral souvenirs and it's white that's dead or dying coral usually and when we see these beautiful colorful coral reefs that is live coral that that has this symbiotic relationship intact with the Zo's enthil a interesting fact most coral is not all coral lacks pigment and so all these colors that you see are not actually the corals colors the coral is somewhat translucent and the color that you're seeing actually comes from the many species of those anthalie these microscopic algae that live inside of the coral and so when the coral has lost all of its color and it's white that is a symbol that's a it's a sign that the symbiotic relationship has been broken that the those anthalie are missing so why are the zooxanthellae gone why why are we seeing bleaching events all throughout the ocean well one of the interesting reasons that coral bleaching events have been happening this is a relatively new development development in the last few years it was discovered that coral reefs oval corals were actually expelling those anthalie so they were essentially spitting it out and why were they doing this they they have and and they haven't adapted them to expel those ants away when too much when they get this chemical signal that too much photosynthesis is happening so but there's too much photosynthesis happening there are there's a buildup of certain chemicals inside of the coral and it can be a little bit toxic and so over time throughout evolution there's this adaptation in in the populations where when there's when they get this chemical signal that too much photosynthesis is happening they spit out the zooxanthellae when the idea is that some of the zooxanthellae will come back in recolonize and you'll have nice manageable levels of photosynthesis well the thing is what what scientists believe now is that the coral is misperceiving the chemical changes in the ocean water that are happening because of uptake of co2 and other greenhouse gases there misperceiving this chemical change as a buildup of too much photosynthesis product and so they're expelling all of their zones anthalie well the thing is they can keep expelling as as an delayed that chemical signature is not going away because it's not coming from the zooxanthellae and so they continue to spit out the their symbiotic algae and then eventually they die and become bleached and so that's that's the the kind of the latest development in understanding why coral bleaching events are happening so really really important symbiotic relationship really important a neutralist ik relationship between the coral and the zones anthony the microscopic algae and and so so i wanted to talk a little bit about not just the effects on coral right but I've already said that coral reef systems support up to 50 percent of the biodiversity of the ocean and so you would imagine that there would be a serious effect of coral bleaching events on other organisms in the ocean right and in fact there are and this these figures right here are showing you first on the top over time from 1996 2003 this is just when a set of surveys were done a reduction in coral cover the percent coral cover in an area and then below you're seeing a similar a correlated reduction in fish species richness so the number of species of fish goes down along with the the percent coral cover and so we do see a drop in biodiversity associated with less live coral cover around the world and the reason I have the term multiple stresses up here also I want to explain what that means and most of the stories I'm going to tell you most of the environmental problems out there if not all of them are not due to one thing there's not one factor that's causing these problems and in fact most of these populations that are declining most of these community communities that are collapsing are doing so because of what we call multiple stressors so there are multiple problems that are causing the decline so I already told you about three or four different threats to reef building corals we would consider those things multiple stressors okay so we I explained how how some people believe that coral are a keystone species right because they take up relatively a relatively small amount of space in the ocean less than 0.01 to five percent and support up to 50 percent of the biodiversity of the ocean I explained this important symbiotic relationship between the coral and the microscopic algae the zooxanthellae and this brings us to the last thing and I'm sorry that got cut off here let's move this over a little this things to the last concept that I've been meaning to tell you about now which is foundation species so coral in addition to being in addition to being a keystone species is also considered a found patience pcs so a foundation species is what it sounds like it's a species that provides the foundation for an ecosystem and it's usually it's usually the most predominant thing in that system and so it's the the species that we tend to characterize the system by so what I like to say is we if you think about a lot of ecosystems that you know that you've heard of coral reef ecosystems the kelp forest ecosystems that I already told you about in college Woods we have beautiful hemlock forests right we name the ecosystem usually after the foundation species so hemlock is the foundation species in a hemlock forest coral are the foundation species in coral reef ecosystems kelp is the foundation species in a kelp forest ecosystem and so these are the species that provide usually the physical structure for the system the physical like how to tab structure division of space for an ecosystem and I don't think I've said this yet so I want to make a point of saying it one of the one of the reasons that we have such great biodiversity in coral reef systems right like here and in kelp forest systems is because of this amazing structure that is provided by the foundation species so the more structure you have the more the more you can partition the space the more species can be can coexist there right because it reduces a conflict and competition it creates lots of different niches and territories it provides more substrate for more food to grow on like phytoplankton periphyton rather that grows on other surfaces there are all sorts of reasons that structure can benefit a community and can increase biodiversity so anything again that creates more division of space is probably going to lead to to greater biodiversity all right so multiple stressors this idea that we have multiple things that are causing problems for species for ecosystems so with coral reefs we have pollution of all kinds that's already multiple stressors but then on top of pollution such as greenhouse gases and course social acidification that results from that so there's that there's fisheries practices that cause physical harm to coral reefs there's direct over harvesting by humans and those are just a few of the multiple stressors affecting coral reefs we talked about symbiosis and specifically the mutualistic relationship the mutualism between the coral the refillable corals and the microscopic algae and we talked about coral as keystone species and we talked about coral as a foundation species and of course we looked at these ecosystem effects of removing foundation species and keystone species from systems and I just want to remind you one more time about this other case study that we looked at with the sea otter perch in kelp forest story so it's from this story the sea otter is a keystone species the kelp the giant kelp is the foundation species so that's a little bit different from the coral system that we just heard about where the coral is both the keystone and the foundation species so there's when I drive that point home because I know that's a point of confusion for some people