## 3 Results
### Submerged vs. Emerged Primary Production and Its Predictors  
To investigate the relative importance of submerged and emerged primary production and if this differed over a gradient of water column turbidity, primary production measures as a function of site and tidal period during T3 were compared (Figure 4). At the three sites with the highest water column turbidity (MNK-L, MNK-R and RAG), submerged NPP was significantly lower than emerged NPP and negative at the two most turbid sites (MNK; Table 4). In contrast, at the three sites receiving the greatest light availability, submerged NPP was equal to or greater than emerged NPP. The relationship between GPP and water column turbidity was weaker, with emerged GPP at the three most turbid sites being only slightly greater than or equal to emerged GPP from the least turbid sites (Figure 4B). After standardising GPP by incident PAR, submerged GPPi did not strongly relate to water column turbidity. This may be partially attributed to the low incident light recorded at RAG (Figure 2D). Emerged GPPi was highly variable among sites and did not significantly exceed submerged GPPi (Table 4). Emerged GPPi was considerably higher at TAU-O when compared to the other sites, however, this is likely to be an artefact of both low light availability during the emerged sampling, and high incident light during the submerged sampling event (Figure 2D). Photosynthetic efficiency (GPPSed + chla: correcting GPP by PARSed and photosynthesising biomass (chl _a_)) appeared to be independent of water column turbidity during submerged tidal periods, with little difference observed among sites (Figure 4D). The only exception occurred at MNK-R where photosynthetic efficiency was notably higher. Submerged GPPSed + chla was greater than emerged GPPSed + chla at all but one site (TAU-O) where photosynthetic efficiency was equal between tidal periods. Figure 3: Effect of nutrient enrichment on control normalised net primary production (NPP) (**A,B**) and gross primary production (GPP) (**C,D**) during submerged and emerged tidal periods, respectively. Data are pooled across sites and green boxes represent data from T1 (November 2017 where no emerged data were collected) and black boxes from T3 (November 2018). Boxes are the 25 th and 75 th percentiles, and whiskers the 5 th and 95 th percentiles. The dotted line is provided as a reference to control values. These relationships appear to be relatively robust through time at the three sites where a June comparison is available (Figure 5). Submerged NPP was lowest at the most turbid site (RAG) during T2 and T3, and significantly lower than emerged NPP compared to sites with higher light availability (TAU-O and TAU-T). Emerged NPP at RAG was significantly higher than both TAU sites during both sampling dates (Table 5). All GPP estimates showed no clear relationship with time, however, RAG was observed to have the lowest submerged GPP and highest emerged GPP across both sampling dates. Once corrected for incident light, submerged GPP\({}_{\rm i}\) was three times higher at TAU-O, compared to all other sites and across the two sampling dates, while all other submerged GPP\({}_{\rm i}\) fluxes were relatively consistent. Photosynthetic efficiency remained significantly higher during submergence at all sites and sampling dates except for RAG during T2 and TAU-O during T3 where similar estimates between tidal periods were observed. Figure 4: Net primary production (NPP) (**A**), gross primary production (GPP) (**B**), gross primary production corrected by PAR\({}_{\rm i}\) (GPP\({}_{\rm i}\)) (**C**), and gross primary production corrected by PAR\({}_{\rm Sed}\) and photosynthetic biomass (sediment chl \(a\) content) (GPP\({}_{\rm Sed+chla}\)) (**D**), during emerged (red) and submerged (blue) tidal conditions in November 2018 (T3). Bars represent means (n = 9) with standard error bars displayed.