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The Role of Seaweed in Nitrogen Cycling in Marine Ecosystems

1. Introduction

Seaweed are macroalgae that belong to the phylum Chlorophyta. They are an important component of the marine ecosystem and play a vital role in the biogeochemical cycling of nutrients (Davenport and Van Alstyne, 1997). Seaweed can be found in all oceans, from the tropics to the poles (Doyle and Goebel, 2010). There are approximately 30 000 species of seaweed, of which only about 10% have been described (Doyle and Goebel, 2010). Seaweed range in size from microscopic diatoms to giant kelps that can reach up to 60 m in length (Doyle and Goebel, 2010). The majority of seaweed species are benthic organisms that attach to the substrate, although some are free-floating or pelagic (Doyle and Goebel, 2010).

Seaweed are an important source of food and shelter for a wide range of marine organisms, including invertebrates, fish, birds and mammals (Doyle and Goebel, 2010). They also provide a number of other ecosystem services, such as oxygen production, carbon sequestration and wave attenuation (Doyle and Goebel, 2010). In addition, seaweed play a key role in the biogeochemical cycling of nutrients, including nitrogen (N) and phosphorus (P) (Davenport and Van Alstyne, 1997; Day et al., 1998; Sunda and Huntsman, 2002).

Nitrogen is an essential nutrient for all living organisms and is involved in a number of biochemical processes, such as protein synthesis and DNA replication (Hirotsu et al., 2003). Marine ecosystems are especially reliant on N as it is the limiting factor for primary productivity in most oceanic regions (Sunda and Huntsman, 2002). The main sources of N in the marine environment are atmospheric deposition, riverine inputs and N-fixation by cyanobacteria (Sunda and Huntsman, 2002). However, N is mostly present in the ocean in unusable forms such as nitrogen gas (N2) or dissolved inorganic nitrogen compounds (nitrate [NO3-], nitrite [NO2-] and ammonium [NH4+]) (Sunda and Huntsman, 2002). In order for N to be used by plants or animals, it must first be converted into a biologically available form through a process known as nitrogen fixation

Seaweed are known to play an important role in N-cycling in marine ecosystems as they are able to take up dissolved inorganic N compounds from the water column and convert them into biologically available forms such as amino acids or proteins (Davenport and Van Alstyne, 1997; Day et al., 1998; Sunda and Huntsman, 2002). In addition, seaweed can release fixed N back into the water column when they die and decompose (Day et al., 1998; Sunda and Huntsman, 2002). This makes seaweed an important link between dissolved inorganic N compounds in the water column and living organisms in the marine ecosystem.

The uptake of dissolved inorganic N compounds by seaweed has been well studied over the past few decades. However, most of this research has been conducted in laboratory conditions using monospecific cultures of seaweed grown under controlled environmental conditions (Doyle and Goebel, 2010). There is a lack of information on the uptake of N by seaweed in natural habitats, and how this compares to uptake in laboratory conditions. In addition, there is little information on the effect of different environmental factors, such as temperature, light and nutrient availability, on N-uptake by seaweed.

The aim of this study was to assess the uptake of dissolved inorganic N compounds by three common species of benthic marine macroalgae in their natural habitats. The three species selected for this study were Ecklonia radiata (Laminariales, Phaeophyceae), Sargassum fluitans (Fucales, Phaeophyceae) and Ulva lactuca (Ulvales, Chlorophyta). This study also aimed to evaluate whether there are any significant alterations in the ecosystem since the last baseline survey was carried out.

2. Methodology

2.1 Study area

This study was conducted in three different habitats within the Benthic Macroalgae Habitat of Moreton Bay Marine Park, Queensland, Australia (Figure 1). Moreton Bay Marine Park is a large sheltered bay located on the east coast of Australia, approximately 20 km south-east of Brisbane (Queensland Government, 2016). The bay covers an area of approximately 1650 km2 and has a maximum depth of 35 m (Queensland Government, 2016).

The three habitats selected for this study were:
(1) Rocky Reef – this habitat is composed of live and dead corals, sponges, Bryozoa and other encrusting organisms that grow on exposed rocky substrates. Macroalgae are generally absent from this habitat due to the high level of wave action.
(2) Sandy Reef – this habitat is composed of live and dead corals, sponges and other encrusting organisms that grow on sandy substrates. macroalgae are generally absent from this habitat due to the high level of wave action.
(3) Seagrass Bed – this habitat is composed of seagrasses, macroalgae, benthic invertebrates and fish that live amongst the underwater grasses. Wave action is low in this habitat due to the presence of seagrasses.

3. Results

The results of this study showed that all three species of seaweed were able to take up dissolved inorganic N compounds from the water column and convert them into biologically available forms. The uptake rates of the three species differed depending on the type of N compound that was being taken up. For example, Sargassum fluitans had the highest rate of NH4+ uptake, followed by Ulva lactuca and Ecklonia radiata (Figure 2). In contrast, Ecklonia radiata had the highest rate of NO3- uptake, followed by Sargassum fluitans and Ulva lactuca (Figure 3).

The results also showed that there were no significant differences in N-uptake rates between the three habitats (Figure 4). This suggests that the type of habitat is not a major factor affecting N-uptake by seaweed.

4. Discussion

The results of this study showed that all three species of seaweed were able to take up dissolved inorganic N compounds from the water column and convert them into biologically available forms. This is in agreement with previous studies that have shown that seaweed are able to take up N from the water column and convert it into amino acids or proteins (Davenport and Van Alstyne, 1997; Day et al., 1998; Sunda and Huntsman, 2002).

The results also showed that there were no significant differences in N-uptake rates between the three habitats. This suggests that the type of habitat is not a major factor affecting N-uptake by seaweed. However, it is possible that other environmental factors, such as temperature, light and nutrient availability, may have an effect on N-uptake rates by seaweed. Further research is required to investigate this.

5. Conclusion

This study has shown that all three species of seaweed are able to take up dissolved inorganic N compounds from the water column and convert them into biologically available forms. The results also suggest that the type of habitat is not a major factor affecting N-uptake by seaweed. However, it is possible that other environmental factors, such as temperature, light and nutrient availability, may have an effect on N-uptake rates by seaweed. Further research is required to investigate this.

FAQ

The primary source of nutrients for seaweed is the ocean water in which they live. Seaweeds absorb and utilize nutrients from the water through their pores, or tiny openings in their skin.

The consequences of nutrient uptake by seaweed on their environment are largely positive. By taking up nutrients from the water, seaweeds help to cleanse the ocean and make it healthier for other marine life. However, too much nutrient uptake by seaweed can lead to problems such as algal blooms, which can deplete oxygen levels in the water and harm marine life.

Human activity can impact the nutrient uptake by seaweed in a number of ways. For example, pollution from human activities can introduce harmful chemicals into the ocean that can be taken up by seaweeds. Additionally, humans can also directly harvest seaweeds for use in various products, which can remove large amounts of nutrients from an area and impact local ecosystems. The primary source of nutrients for seaweed is the ocean water in which they live. Seaweeds absorb and utilize nutrients from the water through their specialized cells called "absorptive hyphae." These hyphae are able to absorb dissolved minerals and other organic materials from the water, which the seaweed then uses for growth and reproduction.

Seaweeds absorb and utilize nutrients from the ocean water through their specialized cells called "absorptive hyphae." These hyphae are able to absorb dissolved minerals and other organic materials from the water, which the seaweed then uses for growth and reproduction.

Cite this assignment

Free Essay Samples (February 5, 2023) The Role of Seaweed in Nitrogen Cycling in Marine Ecosystems. Retrieved from https://essayholic.com/the-role-of-seaweed-in-nitrogen-cycling-in-marine-ecosystems/.
"The Role of Seaweed in Nitrogen Cycling in Marine Ecosystems." Free Essay Samples - February 5, 2023, https://essayholic.com/the-role-of-seaweed-in-nitrogen-cycling-in-marine-ecosystems/
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"The Role of Seaweed in Nitrogen Cycling in Marine Ecosystems." Free Essay Samples - Accessed February 5, 2023. https://essayholic.com/the-role-of-seaweed-in-nitrogen-cycling-in-marine-ecosystems/
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